Bismuth composition for metal pretreatment applications

Abstract

To provide an improved chemical conversion coating. [Solution] An acidic aqueous bismuth conversion coating composition is provided, comprising A) dissolved and / or dispersed bismuth, B) at least one water-soluble organic chelating agent present in an amount sufficient to solubilize or disperse A), and C) dissolved copper ions, and having a pH in the range of about 2.0 to about 6. Furthermore, a method for producing the bismuth conversion coating composition, a method for depositing the bismuth conversion coating onto a metal substrate, and a product having a metal surface containing the bismuth conversion coating are also provided.

Description

[Technical Field]

[0001] The present invention relates to bismuth compositions, for example, chemical conversion coating compositions for metal pretreatment applications, for example, deposition on metal surfaces to improve corrosion resistance and / or paint adhesion, methods for preparing the compositions, methods for coating metal substrates, and products having metal surfaces coated with the compositions. [Background technology]

[0002] Many consumer goods and industrial products are formed from metal substrates and are exposed to these elements. Therefore, these metal products are exposed to corrosive environments. Consequently, they are often coated with protective coatings, including anti-corrosion coatings and paints. Many of these anti-corrosion coatings are known as chemical conversion coatings, and in the art, are understood to be coatings formed by bringing a metal surface into contact with a reactive coating composition, thereby forming a chemical conversion coating on it. While these chemical conversion coatings improve the corrosion resistance of metals, further improvements in chemical conversion coatings are a continuing market requirement for automotive and white goods applications.

[0003] A typical process for applying a chemical conversion coating layer onto a metal substrate includes steps of cleaning, rinsing, and depositing the chemical conversion coating, as well as optional post-rinsing and / or sealing. The metal substrate, at least partially coated with the chemical conversion coating layer, is then subjected in most cases to a painting process (e.g., by electrophoretic coating, also known as E-coating).

[0004] Conventional tricationic zinc phosphate conversion coating systems offer excellent corrosion resistance and paint adhesion, but they contain undesirable heavy metals and generate environmentally harmful waste through the precipitation of heavy metal phosphate sludge. These sludges, as well as overflows from the zinc phosphate bath, contain high concentrations of phosphate ions, both of which can contribute to the eutrophication of natural water sources. Since the zinc phosphate bath is also operated at high temperatures, energy consumption is increased. Therefore, it would be desirable to reduce or avoid the disadvantages of the zinc phosphate process while achieving comparable corrosion resistance and paint adhesion. Zirconium-based conversion coatings have been proposed as alternatives to tricationic zinc phosphate, but in some applications, these conversion coatings do not meet industry requirements, particularly those of the automotive industry. [Overview of the project] [Problems that the invention aims to solve]

[0005] Therefore, the development of alternative chemical coatings and methods would be highly desirable. [Means for solving the problem]

[0006] A bismuth conversion coating composition was developed for depositing a bismuth conversion coating on a metal substrate. Metal substrates pretreated with the aqueous bismuth conversion coating composition and subsequently coated with paint, particularly E-coat paint, showed improved corrosion resistance and paint adhesion to a level comparable to that of tricationic zinc phosphate controls.

[0007] The bismuth conversion coating composition may be applied to the metal surface of a substrate by dipping (immersion) the substrate in an aqueous solution or by spraying the solution onto the substrate. Alternatively, the coating composition may be applied by roll coating or other known conversion coating deposition methods.

[0008] A preferred embodiment of the bismuth conversion coating composition provides a bismuth conversion coating with corrosion resistance and paint adhesion comparable to conventional tricationic zinc phosphate compositions, while improving the reduction of environmental impact due to: absence of heavy metals, such as Zn, Ni, and Mn; absence of phosphorus; and lower operating temperature.

[0009] Some applications of bismuth chemical conversion coating compositions include coating metal substrate surfaces, such as iron, zinc-containing, aluminum-containing surfaces, and combinations thereof, which are subsequently painted and require paint adhesion and corrosion resistance. Suitable applications may include automotive OEM (body-in-white), transportation such as automotive parts; energy industries, such as wind and solar power equipment; agricultural and construction machinery; RVs; construction; household goods such as home appliances; office furniture; metal coils; and metal containers.

[0010] According to one aspect of the present invention ("Aspect 1"), A) Dissolve and / or disperse bismuth, B) At least one water-soluble organic chelating agent present in an amount sufficient to solubilize or disperse A), C) Dissolved copper ions, A chemical conversion coating composition is provided which includes, or is essentially composed of, an acidic aqueous bismuth conversion coating composition containing, and which has a pH in the range of about 2.0 to about 6.

[0011] Embodiment 2: The acidic aqueous bismuth chemical coating composition according to Embodiment 1, wherein A) comprises at least one dissolved Bi(III) and a dissolved and / or dispersed bismuth compound; and B) comprises one or more water-soluble organic acids and salts thereof.

[0012] Embodiment 3: An acidic aqueous bismuth chemical coating composition according to Embodiment 2, wherein one or more water-soluble organic acids and salts thereof are selected from aliphatic or aromatic; linear, branched or cyclic; saturated or unsaturated C3-C12 organic acids and salts thereof.

[0013] Aspect 4: The acidic aqueous bismuth conversion coating composition according to Aspect 2, wherein the one or more water-soluble organic acids and salts thereof include at least one organic polycarboxylic acid and a salt thereof.

[0014] Aspect 5: The acidic aqueous bismuth conversion coating composition according to Aspect 4, wherein the at least one organic polycarboxylic acid and salt thereof include substituted and / or unsubstituted alpha,omega-dicarboxylic acids.

[0015] Aspect 6: The acidic aqueous bismuth conversion coating composition according to Aspect 5, wherein the substituted and / or unsubstituted alpha,omega-dicarboxylic acids and salts thereof include one or more substituted and / or unsubstituted propanedioic acid, butanedioic acid, pentanedioic acid, hexanedioic acid, heptanedioic acid, octanedioic acid, nonanedioic acid, decanedioic acid, and salts thereof.

[0016] Aspect 7: The acidic aqueous bismuth conversion coating composition according to Aspect 2, wherein the one or more water-soluble organic carboxylic acids and salts thereof include tartaric acid and a salt thereof.

[0017] Aspect 8: The acidic aqueous bismuth conversion coating composition according to Aspect 1, comprising less than 1% by weight of phosphorus-containing acid and / or a salt thereof and less than 1% by weight of nickel.

[0018] Aspect 9: The acidic aqueous bismuth conversion coating composition according to Aspect 1, comprising one or more additional components selected from the group consisting of sources of free fluoride, nitrate, and Si-based substances.

[0019] Aspect 10: The acidic aqueous bismuth conversion coating composition according to Aspect 1, wherein the acidic aqueous bismuth conversion coating composition comprises at least one pH adjuster and has a pH of from about 2.5 to about 5.0.

[0020] Aspect 11: The acidic aqueous bismuth conversion coating composition according to Aspect 1, wherein dissolved and / or dispersed bismuth is present at a total concentration of from about 5 to 10,000 ppm.

[0021] Aspect 12: The acidic aqueous bismuth conversion coating composition according to Aspect 1, wherein the dissolved and / or dispersed bismuth comprises one or more of nitrates, oxides and hydroxides of bismuth.

[0022] Aspect 13: The acidic aqueous bismuth conversion coating composition according to Aspect 1, wherein the dissolved and / or dispersed bismuth is selected from bismuth nitrate, bismuth nitrate pentahydrate, bismuth subnitrate, bismuth oxide, bismuth hydroxide, and combinations thereof.

[0023] Aspect 14: The acidic aqueous bismuth conversion coating composition according to Aspect 1, wherein the at least one water-soluble organic chelating agent is present in a total concentration of about 50 to 100,000 ppm.

[0024] Another aspect of the present invention, comprising, consisting essentially of, or consisting of a replenisher composition for replenishing the aforementioned acidic aqueous bismuth conversion coating composition after use, the replenisher composition comprising a storage-stable composition comprising bismuth, copper, nitric acid, and optionally nitrate.

[0025] Aspect 16: a) contacting a metal surface of a substrate, preferably selected from ferrous metals, zinc-containing metals and aluminum-containing metals, with the aforementioned acidic aqueous bismuth conversion coating composition for a time sufficient to form a bismuth conversion coating layer on at least a portion of the metal surface, and b) rinsing the bismuth conversion coating layer with a rinsing solution comprising water, Another aspect of the present invention, comprising, consisting essentially of, or consisting of a method for depositing a bismuth conversion coating on a substrate having a metal surface, the method comprising the foregoing.

[0026] Aspect 17: The method of depositing a bismuth conversion coating according to Aspect 16, further comprising step c) coating at least a portion of the metal surface having the bismuth conversion coating layer by cathodically depositable electrophoretic dip coating, wherein after the rinsing step b) and before being coated by the cathodically depositable electrophoretic dip coating, the metal surface is not dried.

[0027] Embodiment 18: Another embodiment of the present invention comprising, or comprising, a substrate having a metal surface thereon which a bismuth conversion coating layer is deposited thereon, wherein the bismuth conversion coating layer comprises bismuth oxide and / or bismuth hydroxide, and further comprises at least one of the elements Cu, Cu(I) and Cu(II).

[0028] Aspect 19: According to yet another aspect of the present invention, a chemical coating composition comprising, or essentially consisting of, an acidic aqueous bismuth chemical coating composition comprising the following is provided: A) Dissolution and / or dispersion of bismuth; B) A complex fluoroacid, preferably fluorosilicic acid, present in an amount sufficient to solubilize or disperse A); C) Dissolved copper ions; and A pH adjuster in the form of an acid, a base, or a buffered acid / base combination, present in an amount sufficient to provide the composition with a pH in the range of approximately 2.0 to 6.0.

[0029] Unless otherwise specified, any combination or subcombination of the embodiments described above is considered to be within the scope of the present invention.

[0030] For various reasons, it is preferable that the aqueous bismuth conversion coating compositions according to the present invention substantially contain fewer of the components used in prior art compositions for similar purposes, as defined above. Specifically, it is increasingly preferable that, independently of each of the preferably minimized components listed below, the aqueous composition according to the present invention contains, when in direct contact with metal in the process according to the present invention, 1.0, 0.5, 0.35, 0.10, 0.08, 0.04, 0.02, 0.01, 0.001, or 0.0002% or less, more preferably the above values ​​in grams per liter, most preferably in ppm: zinc, nickel, cobalt, man. Gun, chromium, cyanide, nitrite ions, organic surfactants, formaldehyde, formamide, urea, hydroxylamine, ammonia, tertiary amines, cyclic amines, e.g., hexamethylenetetraamine; silicates, siloxanes, organosiloxanes, silanes; lanthanide metals, rare earth metals; phosphorus-containing acids and / or salts thereof; sulfur, e.g., sulfates, sulfonic acids; permanganates; perchlorates; boron, e.g., borax, borates; strontium; and / or free chlorides.

[0031] Furthermore, it is increasingly preferable that, independently of each preferably minimized component listed below, the as-deposited bismuth conversion coating and the as-deposited post-treatment according to the present invention contain the following components in amounts of 1.0, 0.5, 0.35, 0.10, 0.08, 0.04, 0.02, 0.01, 0.001, or 0.0002% or less, more preferably in parts per thousand (ppt) of the above values: chromium, cyanide, nitrite ions, organic surfactants, formaldehyde, formamide, urea, hydroxylamine, ammonia, hexamethylenetetraamine; silicates, siloxanes, organosiloxanes, silanes; rare earth metals; phosphorus-containing acids and / or salts thereof; sulfur, e.g., sulfates, sulfonic acids; permanganates; perchlorates; boron, e.g., borax, borates; strontium; and / or chlorides.

[0032] Some materials may be present in the bismuth conversion coating working bath, for example, due to drag-in from a previous process step, elution from the substrate, or inclusion as counterions or contaminants. Non-limiting examples of materials that may be present and are preferably minimized, but are not intentionally added to the bath, include phosphates and silicic acids from cleaner drag-ins; free Cl ions that may be present from water contamination; and Fe, Zn, and Al ions that may elute from the substrate. Possible counterions include ammonia or ammonium ions, alkali metals (NH4) + na + , K + Examples include sulfates.

[0033] The term “paint” encompasses all similar materials that may be designated by more specialized terms such as lacquer, enamel, varnish, shellac, and topcoat, unless otherwise specified or necessarily implied by the context. The simple terms “metal” or “metallic” will be understood by those skilled in the art to mean a material, whether it be an article or a surface, composed of atoms of metallic elements, e.g., iron, zinc, etc. The total amount of metallic elements present in quantities of increasing priority in the order of 55, 65, 75, 85, or 90 atomic percent. The simple term “iron” encompasses pure iron and its alloys (such as steel), and similarly, “zinciferous” and “aluminiferous” encompass pure metals and their respective alloys.

[0034] Unless otherwise indicated in the operating examples or elsewhere, all figures defining the amounts of components, reaction conditions, or component parameters used herein should be understood to be modified in all cases by the term “approximately.” Throughout this description, unless otherwise specified, percentages, parts, and ratio values ​​are in weight or mass; a description of a group or class of materials as suitable or preferred for a given purpose relating to the present invention means that any two or more mixtures of members of the group or class are equally suitable or preferred; a description of a component in chemical terms means the component at the time of addition to any combination specified in the description, or at the time of in-situ generation in the composition by a chemical reaction between one or more existing components in the composition when one or more newly added components are added to other components; a specification of a component in ionic form further means the presence of sufficient counterions to produce electrical neutrality of the whole composition and any substance added to the composition; counterions thus explicitly specified are preferably explicitly specified in ionic form. The counterions are selected as much as possible from among the other defined components; otherwise, such counterions may be freely selected, except to avoid counterions that would be detrimental to the purposes of the present invention; molecular weight (MW) is weight-average molecular weight; the word “moles” means “gram moles,” and the word itself and all its grammatical variations may be used for chemical species defined by all kinds and numbers of atoms present, regardless of whether the species is ionic, neutral, unstable, hypothetical, or a clearly defined molecule and is actually a stable neutral substance; the term “storage stability” should be understood to include solutions and dispersions in which the material does not show a tendency toward visually detectable phase separation over an observation period of at least 100 hours, or preferably at least 1000 hours, without mechanical disturbance, and the temperature of the material is maintained at ambient room temperature (18–25°C).

[0035] Organic materials are understood to represent molecules composed of at least one carbon atom bonded to a hydrogen atom. The carbon may form a chain or cyclic structure and may optionally contain additional bonded atoms and functional groups (e.g., oxygen, silicon, phosphorus, and nitrogen).

[0036] These and other features and advantages of the present invention will become more apparent to those skilled in the art from the detailed description of preferred embodiments. [Modes for carrying out the invention]

[0037] The present invention provides a bismuth conversion coating composition useful for coating the surface of a metal substrate. The aqueous acidic bismuth conversion coating composition comprises, or optionally consists of, the following mixtures: A) preferably containing Bi(III) ions, dissolved and / or dispersed bismuth, optionally dissolved and / or dispersed bismuth compounds; B) Preferably, at least one water-soluble organic chelating agent comprising one or more water-soluble organic acids capable of chelating and / or dispersing bismuth, and preferably increasing its solubility, and which may have a pH in the range of about 2.0 to about 6; C) Copper(II) ion; D) At least one metal etchant, preferably comprising a composite fluoroacid that can provide a reservoir of free fluoride sources, e.g., fluoride-containing compounds such as HF and / or free fluoride ions. The free and composite fluoride ions act to increase etching of the metal substrate surface; E) At least one pH adjuster in the form of an acid, a base, or a buffered acid / base combination, useful for adjusting the pH to the ranges of 2–6, 2.5–5, 2.75–4.5, and 3–4; Optional components of a bismuth conversion coating composition including the following: F) Nitrate ion; G) IVB group metals: Zr, Ti, Hf; H) at least one accelerator; and I) At least one water-soluble and / or water-dispersible polymer compound.

[0038] The aqueous mixture may be in the form of a solution or dispersion, preferably a storage-stable solution or dispersion. As used herein, the term "dispersion" includes mixtures in which none of the components of the mixture are dissolved in an aqueous medium, as well as mixtures in which a part of one or more components of the mixture are dissolved in an aqueous medium.

[0039] Component A), dissolved and / or dispersed bismuth desirably comprises dissolved Bi(III), but may also be supplied from dissolved bismuth metal, dissolved and / or dispersed bismuth compounds, or desirably may be supplied from Bi(V) using a reducing agent useful for reducing the oxidation state of bismuth to Bi(III). Some sources of bismuth may be relatively insoluble in water, and can be useful in the present invention by first dissolving them in an acid or adjusting the pH of the conversion coating composition. Illustrative non-limiting examples of bismuth sources include: bismuth nitrate Bi(NO3)3; bismuth nitrate pentahydrate Bi(NO3)3·5H2O; basic bismuth nitrate Bi5O(OH)9(NO3)4; bismuth oxide Bi2O3; bismuth hydroxide Bi(OH)3; bismuth aluminate Bi2(Al2O4)3; ammonium bismuth citrate C 12 H 22 BiN3O 14 ; bismuth citrate BiC6H5O7 (1:1); potassium bismuth citrate C 12 H8BiK5O 14 ; sodium bismuth tartrate (C4H4O6)2BiNa; sodium bismuth triglycollamate C 24 H 28 BiN4Na7O 25 , sodium nitrilotriacetic acid bismuth complex; basic bismuth acetate CH3COOBiO; basic bismuth carbonate (BiO)2CO3; bismuth carbonate Bi2(CO3)3; bismuth fluoride BiF3; bismuth molybdate Bi2(MoO4)3; basic bismuth salicylate HOC6H4COOBiO (1:1 or 3:1); bismuth sulfate Bi2(SO4)3; bismuth silicate Bi4Si3O 12This includes bismuth compounds such as complex silicates; bismuth hydroxide Bi(OH)3; bismuth tungstate Bi2(WO4)3; and bismuth vanadate BiVO4. Exemplary and non-limiting examples of preferred bismuth sources include Bi compound bismuth oxide, bismuth sulfate, bismuth nitrate, bismuth nitrite, and bismuth materials that are at least partially water-soluble and / or acid-soluble.

[0040] For example, bismuth(V) phosphate, Bi3(PO4)5; bismuth(III) orthophosphate, BiPO4; bismuth bromide, BiBr 3、 BiOBr; bismuth halogens such as bismuth oxybromide, BiOBr; bismuth pentafluoride, BiF5; bismuth trihydrogenate, BiH3; bismuth chloride, BiCl3; bismuth oxychloride, BiOCl; bismuth iodide, Bii3; bismuth oxyiodide, BiOI; similarly insoluble sodium bismuthate, NaBiO3; bismuth oxalate, Bi(C2O4)3; bismuth oleate, [CH3(CH2)7CH=CH(CH2)7COO]3Bi; similarly bismuth butylthiolaurate, CH3, which can release H2S gas when dissolved in acid. 39 Other Bi sources, such as gas generators (CH2)9CH(SC4H9)COOBi(OH)2 and bismuth sulfide Bi2S3, can also be used, but these tend to be undesirable for reasons of their counterions, environmental impact, and / or safety.

[0041] As disclosed herein, Bi(III) that can be adhered to a metal substrate as a chemical conversion coating may be provided, and any inorganic or organic source of Bi(III) in the working bath may be used as long as it does not adversely affect the object and benefit of the present invention. A combination of two or more different bismuth compounds may be used.

[0042] A bismuth conversion coating composition useful in the present invention may have, for example, concentrations of dissolved and / or dispersed bismuth of component A) of about 5 to 10,000 ppm, 15 to 5,000 ppm, 25 to 4,000 ppm, 50 to 3,000 ppm, 75 to 2,000 ppm, 90 to 1,500 ppm, 100 to 1,000 ppm, 200 to 750 ppm, or 250 to 600 ppm. According to an advantageous embodiment of the present invention, a bismuth compound preferred as a source of bismuth(III) is water-soluble. For example, a bismuth compound may have a solubility in water of at least 0.5% by weight, at least 1% by weight, at least 5% by weight, or at least 10% by weight at 25°C. However, in other embodiments, the bismuth compound is dispersible in water, preferably providing a storage-stable dispersion and providing bismuth(III) ions in a bath combined with the bismuth conversion coating composition and / or component B).

[0043] Component B), at least one water-soluble organic chelating agent, preferably comprises one or more water-soluble organic acids and / or salts thereof, preferably substituted and / or unsubstituted organic carboxylic acids, capable of chelating the dissolved and / or dispersed bismuth. In one embodiment, component B) comprises a water-soluble C3-C12, preferably C4-C9 organic acid and / or salt thereof. (Meth)acrylic monomer acids and salts thereof are preferably avoided because they tend to polymerize in the bath. The organic acid may be aliphatic or aromatic; it may be linear, branched or cyclic; it may be saturated or unsaturated and may contain one or more nitrogen-containing functional groups. The water-soluble organic acid may be a monocarboxylic acid, but it is preferable to have di, tri, tetracarboxylic acids (organopolycarboxylic acids) or more carboxyl groups, as long as it does not interfere with the purpose of the present invention. Having multiple carboxyl groups provides multiple donor atoms available for bonding the metal atom. In a preferred embodiment, the organic polycarboxylic acid is at least bidentate, meaning it has two donor atoms that allow it to bond to a central bismuth atom or ion at two points. Compared to two separate donors, monocarboxylic acids, such as formic acid, bidentate donors are entropically favorable. The water-soluble organic acid and / or salt thereof may be substituted with other functional groups, such as hydroxyl groups. In one embodiment, the organic carboxylic acid may be a hydroxyl-functionalized polycarboxylic acid. In further embodiments, the hydroxyl-functionalized polycarboxylic acid may preferably have an OH group to COOH group ratio in the range of about 0.5:1 to 5:1. Preferably, component B) is present in an amount sufficient to solubilize or suspend the Bi ion, for example, about 50 to 100,000 ppm, 100 to 75,000 ppm, 200 to 50,000 ppm, 250 to 25,000 ppm, 300 to 20,000 ppm, 350 to 10,000 ppm, 400 to 75,000 ppm, 450 to 5,000 ppm, or 500 to 3,000 ppm.

[0044] Non-limiting examples of materials suitable for component B) include: organic acids having multiple carboxylic acid functional groups such as alpha,omega-dicarboxylic acids, e.g., propanediic acid, butanediic acid, pentanediic acid, hexanediic acid, heptanediic acid, octanedic acid, nonanediic acid, decanediic acid, etc., which may further contain one or more additional functional groups along the carbon chain, e.g., hydroxyl functional groups. Specific examples of materials suitable for component B) include tartaric acid, citric acid, ethylenediaminetetraacetic acid, etc., as well as lactic acid, gluconic acid, gallic acid, ascorbic acid, bicine (2-(bis(2-hydroxyethyl)amino)acetic acid) and salts of any of these acids, as well as mixtures of one or more organic acids and salts.

[0045] Component C), copper ions, preferably copper(II) ions, may be present in the bismuth conversion coating composition in amounts of about 1-300 ppm, 1.5-200 ppm, 2-150 ppm, 3-100 ppm, 3.5-75 ppm, 4-50 ppm, 4.5-25 ppm, or 5-20 ppm. Non-specific examples of materials suitable for component C) include hexafluorosilicic acid, hydroxides, nitrates, chlorides, phosphates, and sulfates, as well as water-soluble and / or acid-soluble inorganic and organic copper sources such as acetates, citrates, formates, glucons, and tartrates, as well as other organic copper salts, as well as oxides, selenites, and the like. Any inorganic or organic source of Cu(II) can be used, which can dissolve in the conversion coating composition and at least partially deposit on the conversion coating on the metal substrate, resulting in Cu(II) ions that do not adversely affect the objectives and advantages of the present invention. Copper(II) sulfate, copper(II) nitrate, copper(II) oxide, and copper(II) hydroxide are preferred. A combination of two or more different copper compounds may also be used.

[0046] Component D), one or more metal etchants, may include a free fluoride source such as HF and / or a complex fluoroacid, and may exist as a fluoride ion source, preferably a complex fluoroacid or a salt thereof. The complex fluoroacid may be selected from fluoroacids of the general formula H2XF6, where X may be Ti, Zr, Hf, and Si, and salts of these fluoroacids may also be useful in the present invention. Generally, the amount of component D), such as HF, complex fluoroacids, and / or salts thereof, useful in bismuth conversion coating compositions is in the range of about 0 to 5000 ppm, 100 to 4500 ppm, 200 to 4000 ppm, 300 to 3500 ppm, or 400 to 3000 ppm, 450 to 2500 ppm, 500 to 2000 ppm, or 525 to 1500 ppm. Component D) may preferably provide a reservoir of free fluoride ions. Generally, the amount of free fluoride useful in bismuth conversion coating compositions is in the range of approximately 0-5000 ppm, 1-4000 ppm, 3-3000 ppm, 4-2000 ppm, 5-1000 ppm, 6-500 ppm, 8-200 ppm, or 10-100 ppm. Free and complex fluoride ions act to increase etching of the metal substrate surface.

[0047] Component E), the pH adjuster, may be in the form of an acid, a base, or a combination of buffer acid / base. The bismuth conversion coating composition preferably has a pH in the range of 2 to 6. If the pH is less than 2, etching will be excessive, and sufficient film formation will not be possible. If it exceeds 6, etching will be insufficient, resulting in a poor coating film and the precipitation of bath components. More preferably, the lower limit is 2.5 and the upper limit is 5.5. Even more preferably, the lower limit is 3 and the upper limit is 4. Acidic compounds such as nitric acid and sulfuric acid, and basic compounds such as sodium hydroxide, potassium hydroxide, and ammonia can be used to adjust the pH of the conversion coating agent. Methods for adjusting the pH level to the ranges of 2 to 6, 2.5 to 5, 2.75 to 4.5, and 3 to 4 are known to those skilled in the art. The desired pH is preferably set by adding at least one base, more preferably at least one inorganic and / or at least one organic base. Suitable examples of pH adjusters useful for the bismuth chemical coating compositions described herein include NaOH, KOH, ammonium hydroxide, ammonium bicarbonate, ammonium carbonate, sodium bicarbonate, sodium carbonate, potassium bicarbonate, potassium carbonate, and Bi(OH)3.

[0048] Component F), nitrate ions are preferably present and may be provided as counterions or partial counterions to other components of the bismuth conversion coating composition, such as, for example, non-limitingly, component A), and, if present, components D) and F). Suitable sources of component F include nitric acid, bismuth(III) nitrate pentahydrate; bismuth subnitrate, and nitrates of copper nitrate and group IVB metals, with sodium nitrate and nitric acid being preferred if countercations are present. Nitrate ions are preferably present in amounts of about 0-10,000 ppm, 15-9,000 ppm, 30-8,000 ppm, 45-7,000 ppm, 60-6,000 ppm, 75-5,000 ppm, 90-4,000 ppm, 100-3,500 ppm, or 75-3,000 ppm. Any inorganic or organic source of nitrate ions that does not adversely affect the objectives and advantages of the present invention may be used. A combination of two or more different nitrates may be used.

[0049] The bismuth chemical coating composition may include the following additional components:

[0050] Component G), a group IVB metal, may be present in the bismuth conversion coating composition and the resulting coating. Preferably, the group IVB metal may be selected from Zr, Ti, and Hf, and combinations thereof, preferably Zr and Ti. Generally, the amounts of component G) useful in a bismuth conversion coating composition are about 0-500 ppm, 10-450 ppm, 20-400 ppm, 30-350 ppm, 40-300 ppm, 45-250 ppm, 50-200 ppm, and 70-150 ppm. Non-existent examples of materials suitable for component G) include water-soluble and / or acid-soluble inorganic and organic sources of group IVB metals, such as fluorotitanic acid, H2TiF6; fluorozirconic acid, H2ZrF6; zirconium basic carbonate, Zr(OH)2CO3·ZrO2; titanium nitrate, Ti(NO3)4; titanium acetate, Ti(CH3COO)2; zirconium nitrate, Zr(NO3)4; zirconium acetate, Zr(CH3COO)2. Fluoroacids of group IVB metals may also optionally be provided as one or more metal etchants, at least a portion of component D).

[0051] Bismuth chemical coating compositions may contain one or more accelerators, component H). Typically, chemical coating compositions do not require the presence of accelerators for relatively rapid deposition, as shown by examples without accelerators. Optionally, one or more coating accelerators may be included in amounts of 1 to 5000 ppm, preferably oxidation accelerators such as peroxides, iron(III) ions, nitrite ions, hydroxylamine, persulfate ions, sulfite ions, hyposulfite ions, and halogen ions such as sodium chlorate. Non-specific examples of suitable materials for component H include water-soluble and / or acid-soluble accelerators such as hydroxylamine (which may be provided as a salt such as hydroxylamine sulfate); peroxides, preferably hydrogen peroxide; sodium nitrobenzenesulfonate; and sodium nitrite, nitroguanidine, oximes, etc., which can accelerate the deposition reaction of the bismuth chemical coating composition without adversely affecting the working bath or deposition coating. The amount of component H) varies depending on the type of accelerator used, and selecting an appropriate amount is within the knowledge of those skilled in the art of chemical coating technology. Generally, the amount of component H) useful in bismuth chemical coating compositions can be in the range of approximately 0-500 ppm, 10-450 ppm, 20-400 ppm, 30-350 ppm, 40-300 ppm, 45-250 ppm, 50-200 ppm, or 70-150 ppm. Alternatively, in the case of less active accelerators, or accelerators whose concentration decreases rapidly due to decomposition, for example, the upper limit of the accelerator may include concentrations of 1000 ppm, 900 ppm, 800 ppm, 700 ppm, or 600 ppm in addition to the aforementioned ranges.

[0052] Bismuth conversion coating compositions deposit a satisfactory bismuth coating in the absence of polymers, however, component I), one or more water-soluble and / or water-dispersible polymer components may be advantageously included in the bismuth conversion coating composition as needed. Generally, the amounts of component I) useful in bismuth conversion coating compositions range from about 0 to 500 ppm, 10 to 450 ppm, 20 to 400 ppm, 30 to 350 ppm, 40 to 300 ppm, 45 to 250 ppm, 50 to 200 ppm, and 70 to 150 ppm. Non-existent examples of materials suitable for component I) include: (i.1) polyhydroxylalkylamino derivatives of poly{p-hydroxystyrene}, described in detail in U.S. Patent No. 4,963,596, the full disclosure of which is incorporated herein by reference except to the extent contrary to the express statements herein; (i.2) epoxy polymers, in particular polymers of diglycidyl ethers of bisphenol-A, which are optionally capped at the ends with non-polymerizable groups and / or some of the epoxy groups are hydrolyzed to hydroxyl groups; (i.3) polymers and copolymers of acrylic acid, methacrylic acid and their salts; (i.4) organic polymer components selected from phenalkamine compounds, polyamidoamine compounds, catechol compounds and catechol copolymers; and (i.5) silicon-containing polymers and copolymers, which may be organic and / or inorganic polymers.

[0053] As used herein, the term “phenalkamine compound” means a molecule comprising a benzene ring having at least three functional groups bonded to the benzene ring: a) an OH (i.e., hydroxyl) group; b) a C6-C30 saturated or unsaturated alkyl group; and c) an amine-functionalized substituent such as an amino-alkyl substituent. According to one embodiment of the present invention, a phenalkamine compound corresponds to the following formula (I): R-Ar(-OH)-CHR'NHCH2CH2(NHCH2CH2) n NH2(I) In the formula, Ar is a benzene ring, R is a C6-C30 linear or branched saturated or unsaturated alkyl group, R' is H or an alkyl group (for example, a C1-C6 or C1-C3 alkyl such as methyl, ethyl, or propyl), and n is 0, or an integer at least 1, 2, 3, 4, 5, and 20 or less, 18 or less, 16 or less, 14 or less, 12 or less, 10 or less, 8 or less, or 6 or less, preferably 1-4.

[0054] In one embodiment, a) and c) are ortho relative to each other; that is, they are bonded to adjacent carbon atoms of the benzene ring. In a further embodiment, b) is bonded to a carbon atom of the benzene ring that is at least one carbon atom away from each of the carbon atoms to which a) and c) are bonded. In another embodiment, c) is ortho relative to the hydroxyl group, and b) is meta relative to a). The benzene ring may have one or more additional nonhydrogen substituents other than those enumerated in formula (I), e.g., alkyl groups (e.g., methyl, ethyl) and hydroxyl groups (in addition to a). For example, a second optional hydroxyl group may be present on the benzene ring in a meta position relative to c). In one embodiment, the phenalkamine compound may not contain a hydroxyl group that is ortho relative to a). The amine-functionalized substituent c) may include one or more amino groups, preferably primary and / or secondary amino groups, substituted on the alkylene group to which the alkylene group is bonded to the benzene ring. In one embodiment, c) may comprise at least one primary amino group, or optionally two or more primary and / or secondary amino groups. Mixtures or combinations of phenalkamine compounds may also be used. Preferably, the phenalkamine polymer has a weight-average molecular weight in the range of 200 to 2000 daltons. Phenalkamine is further described in concurrently pending International Application No. PCT / 2019 / 065127, which is incorporated herein by reference in whole.

[0055] As used herein, the term “polyamidoamine compound” means a linear or branched saturated or unsaturated organic polymer comprising multiple amide functional groups and optionally amine and / or imidazoline functional groups. The polymer may comprise a tertiary nitrogen atom, multiple branches, and / or at least several imidazoline functional groups having amide bonds to substituents. Preferably, the polyamidoamine polymer has a weight-average molecular weight in the range of 200 to 10,000. Polyamidoamines are described in further detail in International Patent Publication WO2016167928, which is incorporated herein by reference in its entirety.

[0056] The term “catechol compound” means an organic compound having an aromatic ring system that includes at least two hydroxyl groups located on adjacent carbon atoms of the aromatic ring system. As used herein, the term “catechol compound” includes catechol and catechol derivatives such as catecholamines, such as dopamine and 3,4-dihydroxy-L-phenylalanine. “Catechol copolymer” means a reaction product of at least one catechol / catechol derivative and at least one co-reacting compound having one or more functional groups that react with it (wherein the co-reacting compound may be, for example, an amine, a polyamine such as polyethyleneimine, or a (meth)acrylic functionalized compound such as methacrylamideethylethyleneurea), as well as salts and mixtures thereof. Preferably, the catechol copolymer has a weight-average molecular weight in the range of 200 to 10,000 daltons. Catechol, catechol derivatives and polymer reaction products are described in further detail in International Patent Publication WO2018119368, which is incorporated herein by reference in its entirety.

[0057] Other additives known in metal pretreatment techniques may be included in the bismuth conversion coating compositions disclosed herein, provided that the additives do not interfere with the deposition and performance of the bismuth conversion coating. Examples of additives include surfactants, oxidizing agents (different from accelerators), thickeners, rheology modifiers, dispersants, biocides, biostats, and adhesion promoters.

[0058] Certain materials, such as metallic elements, may be present in the bismuth conversion coating composition as additives or contaminants, including metals of Group IIB, VB-VIIB, Group VIII, Group IIIA, and Group IVA, and Sb. These metallic elements may be used as additives, provided that the additives do not interfere with the deposition and performance of the bismuth conversion coating. In some embodiments, such metals are intentionally omitted from the bismuth conversion coating compositions disclosed herein, but may be present as unavoidable contaminants.

[0059] Brighteners such as plating brighteners, for example, naphthalenedisulfonic acid, diphenylsulfonate, arylsulfonamide, and azo dyes, are not preferred, but may be included as optional components in the bismuth conversion coating compositions disclosed herein, as long as the brightener does not interfere with the deposition and performance of the bismuth conversion coating. In preferred embodiments of the bismuth conversion coating compositions disclosed herein, brighteners are absent and are generally omitted due to the cost of the product.

[0060] Manufacturing method The bismuth conversion coating compositions of the present invention may be prepared using any suitable technique known in the art. In one embodiment, the bismuth conversion coating composition is prepared by B) combining at least one water-soluble organic chelating agent with water, preferably distilled water, followed by A) adding a source of dissolved and / or dispersed bismuth while stirring to form a mixture. The pH of the mixture is then adjusted to a selected bath operation pH value.

[0061] In a preferred embodiment, B) may contain one or more water-soluble organic acids, and the pH may be adjusted to a range of about 2 to 6, preferably by adding an alkaline substance, such as a diluted solution of ammonium bicarbonate. Other alkaline sources, such as sodium hydroxide, may be used to raise the pH, provided that they do not interfere with the deposition and performance of the chemical coating.

[0062] After adjusting the pH according to the operating conditions, the chemical coating composition preferably contains Bi(III) ions and may also contain a colloidal dispersion of bismuth particles. The bismuth chemical coating composition may contain anions of dissociated water-soluble organic chelating agents based on the operating pH.

[0063] As used herein, the term “storage stability” when referring to a mixture (whether a solution or a dispersion) means that, after being stored in a sealed container at 20°C for an observation period of at least 3 months, the mixture is not mechanically disturbed, does not exhibit phase separation, and does not show any precipitation or sedimentation of material visible to the naked eye.

[0064] According to aspects of the present invention, an aqueous mixture of at least one bismuth conversion coating composition is brought into contact with the surface of a bare metal substrate. Such an aqueous mixture (which may be in the form of a solution or dispersion, and is preferably a storage-stable mixture) may be formed by any suitable method. For example, the aqueous mixture may be used directly or after diluting the aqueous mixture to a specific desired final use concentration. Only water may be used for such dilution, but in other embodiments of the present invention, one or more other types of components may be included in the aqueous mixture. For example, an acid, a base or a buffer may be combined with the aqueous solution to change its pH characteristics. In certain embodiments of the present invention, the pH of the aqueous mixture when in contact with the surface of a bare metal substrate (i.e., when used in a working conversion coating bath) may be, for example, 2 to 6, 2.5 to 5, 2.75 to 4.5, or 3 to 4.

[0065] Aqueous mixtures (working baths) that repeatedly come into contact with a bare metal substrate surface may experience a decrease in the concentration of bismuth compounds and other components such as copper over time. When this occurs, the aqueous mixture in the working bath may be replenished by adding a supplement containing individual components or combinations of components whose amounts need to be adjusted to provide an effective amount of bismuth compounds, etc., to restore the desired concentration. The compositions according to the present invention may be provided in two packs, in which case Part A may contain, for example, bismuth, copper, and other components that do not form precipitates with Bi and / or Cu, such as nitric acid and / or chelating agents, and Part B may contain chelating agents, fluoride-containing compounds and other components. In one embodiment, the supplement for a bismuth chemical coating bath contains bismuth, copper, and nitric acid and is optionally in the form of an easily dispersible slurry. Furthermore, it is understood that repeatedly used work baths containing aqueous mixtures may accumulate some of various components carried over from the cleaning stage, such as alkaline builders (sodium hydroxide, potassium hydroxide, alkali metal carbonates, alkali metal bicarbonates, phosphates, silicates), surfactants, and oil / grease / dirt contaminants. When the levels of such components reach a point where they adversely affect the performance of the work bath or the quality of the chemically coated metal substrate during treatment, the contents of the work bath can be discarded and replaced, or treated to remove or reduce such components, or to counteract their effects in other ways (e.g., by pH adjustment and / or ion exchange).

[0066] Metal substrate The present invention is particularly useful in relation to the treatment of corrosion-prone metal substrate surfaces, especially bare metal surfaces that are painted. For example, iron (iron-containing) metal substrates may be treated according to the present invention. Exemplary metal substrates include, but are not limited to, iron; steel substrates such as cold-rolled steel, hot-rolled steel, and stainless steel; steel coated with zinc alloys such as zinc metal, electro-galvanized steel, galvalume, galvanyl, and hot-dip galvanized steel; magnesium alloys; aluminum alloys, and aluminum-plated steel substrates. Parts or articles comprising two or more metal substrates can be treated according to the procedures described herein. The present invention may also be carried out using metal substrates in which an iron-containing component or layer is covered with an iron-free metal coating (e.g., a zinc coating), and the iron-containing component or layer is exposed as a result of cutting, shaping, mounting, sanding, grinding, polishing, scoring, or other similar operations.

[0067] Washing process As used herein, the term “bare metal substrate surface” means a metal surface of a metal substrate that is essentially free of any contaminants, is not chemically coated, or is not coated with any substance other than native oxides that may exist due to the reaction of metal elements with oxygen in the atmosphere. According to certain aspects of the present invention, a bare metal substrate surface pretreated with a bismuth chemical coating composition is obtained by cleaning the metal substrate surface to remove grease, oil, dirt, or other foreign matter and contaminants using any cleaning procedure and materials known or conventionally used in the art, for example, weakly alkaline or strongly alkaline cleaning agents, neutral cleaning agents, and acidic cleaning agents. Methods for cleaning metal surfaces are described, for example, in Murphy, “Metal Surface Treatment, Cleaning,” Kirk-Osmer Encyclopedia of Chemistry and Technology, 2000. Aqueous and non-aqueous (i.e., organic solvent-based) cleaning agents may be used. Suitable cleaning agents may include, for example, inorganic bases (e.g., alkali metal hydroxides, alkali metal carbonates, alkali metal bicarbonates), builders (e.g., phosphates, silicates), surfactants, water, and organic solvents. Examples of alkaline cleaning agents include Parco® Cleaning Agent ZX-1, Parco® Cleaning Agent 315, and Bonderite® C-AK T51, which are available from Henkel Corporation in Madison Heights, Michigan. The cleaning agent may be applied to and brought into contact with the metal substrate surface using any suitable method, such as spraying, immersion, or wiping. The optimal temperature during contact may be, for example, about 20°C to 60°C, but may be lower or higher, provided that it does not adversely affect the process. The contact time between the cleaning agent and the metal substrate may be any time effective in achieving the desired degree of contaminant removal (e.g., 10 seconds to 5 minutes). Mechanical action may be utilized to aid in the removal of contaminants. Typically, cleaning agents used for this purpose are in liquid or solution form, but the surface of metal substrates can also be cleaned using only mechanical means such as polishing, sandblasting, or blasting with other drying media.The metal substrate may be subjected to one or more further steps following the cleaning step, before optionally being brought into contact with one or more pre-formed catechol compound / co-reaction compound reaction products in a solution or dispersion. For example, the surface of the metal substrate may be rinsed once or more times with water and / or an acidic aqueous solution after cleaning.

[0068] The bare metal substrate surface may be prepared by methods for forming or finishing a metal article that result in the creation of a bare metal surface, such as cutting, notching, filing, grinding, polishing, shot blasting, and filing.

[0069] Chemical coating process Following any cleaning step, the surface of the metal substrate undergoes a chemical conversion coating step by contacting it with the bismuth conversion coating composition of the present invention. The chemical conversion coating step may be performed immediately after the cleaning step, or after any of the above-described deoxygenation and / or further rinsing steps, or long after the cleaning step.

[0070] According to the present invention, an aqueous mixture containing a bismuth compound is brought into contact with a cleaned surface of a metal substrate. Such contact may be achieved by any suitable method, such as spraying, immersion, dipping, brushing, or roll coating. Typically, the aqueous mixture during such contact is maintained at a temperature ranging from ambient temperature (e.g., room temperature) to a temperature moderately higher than the ambient temperature. For example, the temperature of the aqueous mixture in the working bath may be 10–54°C, 16–49°C, 25–36°C, or 32–43°C.

[0071] The contact time should be selected to be sufficient to deposit an effective amount of bismuth conversion coating onto the bare metal substrate surface and is generally considered an effective amount to reduce the amount of corrosion on the metal substrate surface, as measured according to ASTM B117-19, compared to a bare metal substrate surface control measured under the same conditions. Typically, contact times of 0.1 to 30 minutes (e.g., 8 seconds to 30 minutes, or 10 seconds to 20 minutes, or 30 seconds to 10 minutes, 1 minute to 6 minutes, 1.5 minutes to 3 minutes, or any of the ranges included in the disclosed range) may be selected as appropriate.

[0072] Once the desired contact time with the bismuth conversion coating composition has been reached, contact may be stopped and the conversion-coated metal substrate may be moved to a further processing step. For example, spraying may be stopped or the article containing the conversion-coated metal substrate may be removed from the immersion bath. Any residual or excess aqueous mixture may be discharged from the surface of the metal substrate. Removal of any residual or excess aqueous solution can be achieved by any suitable method or combination of methods such as drip drying, squeezing, wiping, draining, or rinsing with water. According to certain embodiments, the surface of the conversion-coated metal substrate may be dried (e.g., air drying, heating, or oven drying). In other embodiments, the conversion-coated metal substrate is not dried before proceeding to further processing steps such as sealing, painting, etc., by any non-limiting example of electrophoretic coating with paint.

[0073] It has been demonstrated that depositing a bismuth substrate metal and a metal oxide conversion coating onto a metal substrate results in the corrosion resistance of the final painted component being equivalent to that of tricationic zinc phosphate.

[0074] In one embodiment, the bismuth conversion coating composition may be applied to the surface of a reactive metal substrate by contacting the metal substrate with the bismuth conversion coating composition for approximately 2 minutes at a temperature of 24–40°C. Contact may be achieved by any suitable means, including but not limited to dipping, spraying, and roll coating. Contact time and temperature may vary, but are typically less than 10 minutes, preferably less than 5 minutes. Preferably, the contact time is at least about 1 second, 3 seconds, 5 seconds, 10 seconds, 15 seconds, 20 seconds, 30 seconds, 40 seconds, 50 seconds, or 60 seconds, and about 9 minutes, 8 minutes, 7 minutes, 6 minutes, 5 minutes, 4 minutes, 3 minutes, or 2 minutes or less. Preferably, the temperature range is at least about 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, 30°C, 31°C, or 32°C, and not exceeding about 40°C, 39°C, 38°C, 37°C, 36°C, 35°C, 34°C, or 33°C. Higher temperatures up to 50°C, at least above the freezing point of the bath, may be used, as long as they do not interfere with the precipitation of the conversion coating or adversely affect the performance of the metal bismuth conversion coating working bath or the conversion coating.

[0075] Although not bound by a single theory, when a metal substrate is brought into contact with an aqueous acidic bismuth conversion coating composition, several reactions occur: oxidation of the substrate (M 0 →M n+ +n e M = Fe, Zn, Al), H + Due to the local increase in pH caused by reduction, a mixture of the base element (Fe, Zn, Al) and bismuth oxide and / or bismuth hydroxide forms on the metal surface of the base material. 3+ It accumulates.

[0076] Post-processing The present invention may also be part of a multi-step process in which the deposited bismuth conversion coating undergoes post-treatment and / or sealing rinse before painting.

[0077] A non-limiting example of a suitable post-treatment is contacting the as-deposited bismuth conversion coating with an acidic aqueous post-treatment composition (e.g., a zirconium oxide deposition composition) consisting of one or more Group IV metals of the periodic table, such as Zr, Ti, and Hf, and typically also including other components (metal etchants (e.g., fluorides), optionally copper and / or nitrates and / or zinc and / or Si-based substances). The acidic aqueous post-treatment composition may, for example, have a pH of 5.0 or less and may include: at least one Group IV metal in 50-750 ppm; copper in 0-50, 1-50, or 5-50 ppm; free fluorides in 10-100 ppm; optionally, nitrates; optionally, Si-based substances such as silanes, SiO2, or silicates. Optionally, the post-treatment may be a composite post-treatment further comprising dissolved and / or dispersed organic polymers. The acidic aqueous post-treatment composition can be applied to the surface of a metal substrate having a bismuth conversion coating deposited on at least a portion of its surface for a sufficient time to contact the metal substrate with the acidic aqueous post-treatment composition to form a Group IV metal oxide on at least a portion of the metal substrate surface. Contact may be achieved by any suitable means, including but not limited to dipping, spraying, roll coating, etc. Contact time and temperature may vary, but are typically less than 10 minutes, preferably less than 5 minutes. Preferably, the contact time is at least about 1 second, 3 seconds, 5 seconds, 10 seconds, 15 seconds, 20 seconds, 30 seconds, 40 seconds, 50 seconds, or 60 seconds, and about 9 minutes, 8 minutes, 7 minutes, 6 minutes, 5 minutes, 4 minutes, 3 minutes, or 2 minutes or less. Preferably, the temperature range is at least about 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, 30°C, or 32°C, and not exceeding about 40°C, 39°C, 38°C, 37°C, 36°C, 35°C, 34°C, or 33°C. Higher temperatures up to 50°C, at least above the freezing point of the bath, may be used, as long as they do not interfere with the deposition of the chemical coating or adversely affect the performance of the metal bismuth chemical coating working bath or the chemical coating.

[0078] A suitable sealing rinse may preferably be an aqueous rinse, but may optionally contain an organic solvent. The sealing rinse may contain organic polymers, inorganic polymers, or combinations thereof. Typically, the sealing rinse contains a water-soluble and / or water-dispersible polymer that can bond, crosslink, or form a sealing layer on a chemically coated metal substrate upon drying, with or without heating. The sealing rinse may typically have a pH of about 4 to 10.

[0079] Sealing rinse is distinguished from "paint" for the purposes of this invention by the following differences: The thickness of organic sealant rinse is generally about 0.05 to 2.0 microns (wet film), while the thickness of paint film is typically 15 to 500 microns (wet film). The organic sealing layer typically has a dry film thickness of 0.01 to 1.0 microns, as measured by glow discharge emission spectroscopy. The dry film thickness of the paint layer is at least about 15 microns, and is generally 1 mil (25.4 microns), 1.5 mil (38.1 microns) or more, with typical vehicle paints having a total paint thickness of approximately 3-5 mil (76.2 to 127 microns). Organic sealant rinses typically contain up to about 0.5% by weight of organic solids, while paint compositions typically contain at least about 5% to about 60% by weight of organic solids.

[0080] Non-limiting examples of polymers suitable for use in sealing rinses include epoxy, phenol, acrylic, polyurethane, polyester, and polyimide, as well as combinations thereof. In one embodiment, an organic polymer selected from epoxy, phenol, and polyimide is used. Preferred polymers for forming the additional layer include, for example, novolac resins with a formaldehyde-to-phenol molar ratio of less than 1, and phenol-formaldehyde-based polymers and copolymers produced from resol resins with a formaldehyde-to-phenol molar ratio greater than 1. Such polyphenol polymers can be manufactured as known in the art, for example, according to U.S. Patent No. 5,891,952. Novolac resins are preferably used in combination with crosslinking agents to facilitate curing. In one embodiment, a resol resin having a formaldehyde-to-phenol molar ratio of about 1.5 is used to form an additional polymer layer on a bismuth conversion coating. Phenolic resins useful for forming the polymer layer preferably have a molecular weight of about 1000 to about 5000 g / mol, preferably 2000 to 4000 g / mol.

[0081] In some embodiments, the water-soluble and / or water-dispersible polymer may contain functional groups that react with elements in the bismuth conversion coating, potentially forming bonds between the polymer and the coating. For example, uncured novolac and resol resins may contain OH functional groups that can react with metals in the bismuth conversion coating, thereby allowing the polymer to bond to the coating.

[0082] Optionally, Si-based materials such as silane, SiO2, or silicate may be used as sealants or additives. The sealing rinse may be applied to the surface of a metal substrate having a bismuth conversion coating deposited on at least a portion of its surface by contacting the metal substrate with the sealing rinse for a time sufficient to wet the surface of the bismuth conversion coating and / or to form a layer of sealant on at least a portion of the metal substrate surface. Contact may be achieved by any suitable means that further enhance the corrosion resistance of the conversion-coated metal substrate surface.

[0083] Application of additional coating Following a chemical coating and optionally one or more post-rinsing (or "sealing") steps, the metal substrate may be subjected to one or more further processing steps, particularly including the application of paints or other decorative and / or protective coatings. Any such coating known in the art may be used, for example, including electrophoretic coatings (E-coatings), solvent-based paints, water-based paints, powder coatings, etc. In such applications, the bismuth chemical coating or sealer may function as a primer or corrosion-preventive layer.

[0084] Therefore, the present invention may be carried out according to the following exemplary multi-step process: 1) Clean the surface of the metal substrate; 2) Rinse the cleaned (bare) metal substrate surface with an aqueous mixture consisting of a pre-formed catechol compound / functionalized co-reactant reaction product; 3) Apply a chemical conversion coating to the cleaned and rinsed metal substrate surface; 4) Optionally, rinse the chemically coated metal substrate surface with water and / or a post-rinse solution or dispersion; 5) Optionally, the surface of a chemically coated metal substrate is subjected to electrophoretic coating; 6) Rinse the electrophoretic coated metal substrate surface with water; and 7) Bake the rinsed electrophoretic coated metal substrate.

[0085] In this specification, embodiments are described in a manner that allows for a clear and concise description, but it is intended and understood that embodiments can be combined and separated in various ways without departing from the present invention. For example, it should be understood that all preferred features described herein are applicable to all embodiments of the present invention described herein.

[0086] In some embodiments, the inventions herein can be interpreted as excluding elements or process steps that do not substantially affect the basic and novel properties of a composition, article, or method. Furthermore, in some embodiments, the inventions herein can be interpreted as excluding elements or process steps not specified herein.

[0087] While the present invention is illustrated and described herein with reference to specific embodiments, it is not intended to be limited to the details shown. Rather, various modifications can be made in detail without departing from the invention, within the scope of the claims and equivalents. [Examples]

[0088] (Example 1) The following materials were combined and mixed to prepare a chemical coating composition. Deionized water 99.72% by weight Bismuth subnitrate; Bi5O(OH)9(NO3) 40.08% (0.057 wt% Bi) Lactic acid (88% by weight) 0.20% by weight

[0089] The pH of the mixture was 2.7. When the mixture was added to 75% deionized water and 25% of the mixture, the pH rose to 3.1. The pH was further increased using a 10% ammonium bicarbonate solution (Vondelite® M-AD700) until a pH of 3.5 was achieved. This yielded a clear, straw-colored solution containing 143 ppm Bi and 440 ppm Lactic Acid.

[0090] The solution was heated to 32°C. The ACT CRS panel was immersed in the bismuth conversion coating composition (the process outlined below). This resulted in a visibly black coating containing the elements Bi, O, and Fe.

[0091] Panel Coating Process: Bare metal panels, commercially available from ACT Laboratories, were used as coating samples. Unless otherwise specified, the coating process was as follows:

[0092] Bismuth conversion coating process Cleaning solution: Bonderite® C-AK T51 (2% v / v, 49℃, free alkalinity (hereinafter "FAlK") 5.0, 90-second spray, 10 psi) Rinse solution: Tap water (38°C, spray for 60 seconds, 10 psi) Rinse solution: Deionized water (21°C, 60-second spray, 10 psi) Chemical coating: Immerse at 32°C for 120 seconds. Rinse solution: Deionized water (21°C, 60-second spray, 10 psi) E-coat: BASF Casoguard 800 (35°C, 240 seconds immersion, 0.9 Amps constant current ~230V) Rinse solution: Deionized water (24°C, 60-second spray, 10 psi) Paint curing: Oven baking (185°C, 35 minutes).

[0093] Comparative zinc phosphate coating process (Vonderite® M-ZN958) Purchased from ACT Laboratories, Inc. (1.5-2.0 g / m²) 2 A pre-treated zinc phosphate coated panel with a total metal phosphate (phopite and phosphophyllite) coating weight was used. The zinc phosphate coating was applied according to Henkel's technical process publication. Rinse solution: Deionized water (21°C, 60-second spray, 10 psi) E-coat: BASF Casoguard 800 (35°C, 240 seconds immersion, 0.9 Amps constant current ~230V) Rinse solution: Deionized water (24°C, 60-second spray, 10 psi) Paint curing: Oven baking (185°C, 35 minutes).

[0094] Glow discharge emission spectroscopy elemental depth profiles were obtained on panels coated according to the present invention, and the elements present in the coating were identified.

[0095] (Example 2) The following materials were combined and mixed to prepare a chemical coating composition. Deionized water 92.22% by weight Bismuth subnitrate; Bi5O(OH)9(NO3) 40.58% (0.41 wt% Bi) Lactic acid (88% by weight) 7.2% by weight

[0096] The pH of the mixture was 1.97. When the mixture was added to 95% deionized water and 5% of the mixture, the pH rose to 2.7. The pH was further increased using a 10% ammonium bicarbonate solution (Vondelite® M-AD700) until a pH of 3.5 was achieved. This yielded a clear, straw-colored solution containing 209 ppm Bi and 3368 ppm Lactic Acid.

[0097] The solution was heated to 32°C. Using this bismuth conversion coating composition, ACT CRS panels were dip-coated according to the coating process described above. This resulted in a visibly black coating containing the elements Bi, O, and Fe.

[0098] (Example 3) The following materials were combined and mixed to prepare a chemical coating composition. Deionized water 59.95% by weight Fluorosilicate (25% by weight) 40.00% Bismuth oxide; Bi2O3 0.05% (0.045 wt% Bi) pH=1.10 The pH was increased using a 10% ammonium bicarbonate solution (Vondelite® M-AD700) until pH=3.5 was achieved. This resulted in a colorless, transparent solution containing 450 ppm Bi and 10% fluorosilicic acid.

[0099] The solution was heated to 32°C. Using this bismuth conversion coating composition, ACT CRS panels were dip-coated according to the coating process described above. This resulted in a visibly black coating containing the elements Bi, O, and Fe.

[0100] (Example 4) Example 3 was repeated using 0.05% bismuth subnitrate Bi5O(OH)9(NO3)4 instead of 0.05% bismuth oxide Bi2O3 to obtain a mixture with a pH of 1. The pH was increased using a 10% ammonium bicarbonate solution (Vondelite® M-AD700) until a pH of 3.5 was achieved. This yielded a colorless, transparent solution containing 357 ppm Bi and 10% fluorosilicic acid.

[0101] The solution was heated to 32°C. Using this bismuth conversion coating composition, ACT CRS panels were dip-coated according to the coating process described above. This resulted in a visibly black coating containing the elements Bi, O, and Fe.

[0102] (Example 5) Example 3 was repeated using 0.05% bismuth nitrate Bi(NO3)3 instead of 0.05% bismuth oxide Bi2O3 to obtain a mixture with a pH of 1.2. The pH was increased using a 10% ammonium bicarbonate solution (Vondelite® M-AD700) until a pH of 3.5 was achieved. This yielded a colorless, transparent solution containing 253 ppm Bi and 10% fluorosilicic acid.

[0103] The solution was heated to 32°C. Using this bismuth conversion coating composition, ACT CRS panels were dip-coated according to the coating process described above. This resulted in a visibly black coating containing the elements Bi, O, and Fe.

[0104] (Example 6) The following materials were combined and mixed to prepare a chemical coating composition. Deionized water 94.25% by weight Bismuth oxide; Bi2O3 0.5% (0.45 wt% Bi) Tartaric acid 5.25% by weight

[0105] The pH of the mixture was 1.7. When the above mixture was added to 95% deionized water and 5% of the mixture, the pH rose to 2.7. The pH was further increased using a 10% ammonium bicarbonate solution (Vondelite® M-AD700) until a pH of 3.5 was achieved. This yielded a colorless, transparent solution containing 224 ppm Bi and 2625 ppm tartaric acid.

[0106] The solution was heated to 32°C. Using this bismuth conversion coating composition, ACT CRS panels were dip-coated according to the coating process described above. This resulted in a visibly black coating containing the elements Bi, O, and Fe.

[0107] (Example 7) The following materials were combined and mixed to prepare a chemical coating composition. Deionized water 94.17% by weight Bismuth subnitrate; Bi5O(OH)9(NO3) 40.58% (0.41 wt% Bi) Tartaric acid 5.25% by weight

[0108] The pH of the mixture was 1.7. When the mixture was added to 95% deionized water and 5% of the mixture, the pH rose to 2.7. The pH was further increased using a 10% ammonium bicarbonate solution (Bonderite® M-AD700) until a pH of 3.5 was achieved. This yielded a colorless, transparent solution containing 209 ppm Bi and 2625 ppm tartaric acid.

[0109] The solution was heated to 32°C. Using this bismuth conversion coating composition, ACT CRS panels were dip-coated according to the coating process described above. This resulted in a visibly black coating containing the elements Bi, O, and Fe.

[0110] (Example 8) The following materials were combined and mixed to prepare a chemical coating composition. Deionized water 99.30% by weight Bismuth nitrate; Bi(NO3) 30.10% by weight Fluorosilicate (25% by weight) 0.40% Tartaric acid 0.20% by weight

[0111] The pH of the mixture was 2.0. The pH was increased using a 10% ammonium bicarbonate solution (Vondelite® M-AD700) until a pH of 3.5 was achieved. This yielded a colorless, transparent solution containing 506 ppm Bi, 1000 ppm fluorosilicic acid, and 2000 ppm tartaric acid.

[0112] The solution was heated to 32°C. Using this bismuth conversion coating composition, ACT CRS panels were dip-coated according to the coating process described above. This resulted in a visibly black coating containing the elements Bi, C, O, and Fe.

[0113] (Example 9) The following materials were combined and mixed to prepare a chemical coating composition. Deionized water 99.30% by weight Bismuth nitrate; Bi(NO3) 30.10% by weight Fluorosilicate (25% by weight) 0.40% Tartaric acid 0.20% by weight Copper nitrate (1.841%Cu)0.05%

[0114] The pH of the mixture was 2.0. The pH was increased using a 10% ammonium bicarbonate solution (Vondelite® M-AD700) until a pH of 3.5 was achieved. This yielded a clear, slightly blue / green solution containing 506 ppm Bi, 10 ppm Cu, 1000 ppm fluorosilicic acid, and 2000 ppm tartaric acid.

[0115] The solution was heated to 32°C. Using this bismuth conversion coating composition, ACT CRS panels were dip-coated according to the coating process described above. This resulted in a visibly black coating containing the elements Bi, O, C, Cu, and Fe.

[0116] (Example 10) Example 9 was repeated using 0.20% by weight ascorbic acid instead of 0.20% by weight tartaric acid to obtain a mixture with pH=2.0. The pH was increased using a 10% ammonium bicarbonate solution (Vondelite® M-AD700) until pH=3.5 was achieved. This yielded a clear, slightly blue / green solution containing 506 ppm Bi, 10 ppm Cu, 1000 ppm fluorosilicic acid, and 2000 ppm ascorbic acid.

[0117] The solution was heated to 32°C. Using this bismuth conversion coating composition, ACT CRS panels were dip-coated according to the coating process described above. This resulted in a visibly black coating containing the elements Bi, O, Cu, and Fe.

[0118] (Example 11) The following materials were combined and mixed to prepare a chemical coating composition. Deionized water 99.40% by weight Bismuth nitrate; Bi(NO3) 30.10% by weight Fluorosilicate (25% by weight) 0.40% Citric acid 0.10% by weight Copper nitrate (1.841%Cu)0.05%

[0119] The pH of the mixture was 2.0. The pH was increased using a 10% ammonium bicarbonate solution (Vondelite® M-AD700) until a pH of 3.5 was achieved. This yielded a clear, slightly blue / green solution containing 506 ppm Bi, 10 ppm Cu, 1000 ppm fluorosilicic acid, and 1000 ppm citric acid.

[0120] The solution was heated to 32°C. Using this bismuth conversion coating composition, ACT CRS panels were dip-coated according to the coating process described above. This resulted in a visibly gray / black coating containing the elements Bi, O, C, Cu, and Fe.

[0121] (Example 12) A bismuth conversion coating was deposited on an exposed ACT CRS substrate using the following composition and the above coating process with a 32°C coating bath. 1. 450 ppm Bi from Bi2O3, 10% fluorosilicic acid; pH=3.5; 2. 360 ppm Bi from bismuth subnitrate, 10% fluorosilicic acid; pH=3.5; 3. 250 ppm Bi from bismuth nitrate, 10% fluorosilicic acid; pH=3.5; 4. 216 ppm Bi from bismuth subnitrate, 0.3% lactic acid; pH=3.5; 5. 720 ppm Bi, 1000 ppm fluorosilicic acid, 2000 ppm tartaric acid, and 10 ppm Cu from bismuth nitrate; pH=3.5.

[0122] All five of these bismuth conversion coating compositions deposited a dark-colored Bi conversion coating.

[0123] The alkali resistance of these chemical conversion coatings was evaluated by immersion in 0.1M NaOH (pH=12.2) at 21°C for 4 hours. For comparison, bare ACT CRS coated with a commercially available zinc phosphate conversion coating (Bonderite® M-ZN958) was also evaluated using the same test conditions.

[0124] After exposure to NaOH, the panels were rinsed for 30 seconds and air-dried using a clean compressed air source (90 psi). All bismuth-coated ACT CRS panels remained black, showing no signs of rust / iron oxidation. Bismuth loss was approximately 10% of the original weight. The zinc phosphate samples were 100% covered with rust, and the zinc phosphate coating was significantly lost (loss of over 50% of the original weight). In both cases, coating loss was identified using glow discharge emission spectrometry elemental depth profiles (GDOES).

[0125] (Example 13) In this example, different types of ACT metal panels (CRS, EG, HDG, and Al6111 panels) were tested. A bismuth conversion coating composition was prepared according to Example 9, and the pH was increased using a 10% ammonium bicarbonate solution (Vondelite® M-AD700) until pH = 3.5 was achieved. This yielded a clear, slightly blue / green solution containing 506 ppm Bi, 10 ppm Cu, 1000 ppm fluorosilicic acid, and 2000 ppm tartaric acid. The solution was heated to 32°C and had 72 ppm free fluoride and a pH of 3.5.

[0126] Following the application process described above, ACT CRS, EG, HDG, and Al6111 panels were dip-coated. This resulted in a visibly black coating on each of the different metal substrate samples. Each bismuth conversion coating contained the elements Bi, O, C, and Cu, along with the metals from their respective base substrates.

[0127] (Example 14) The following materials were combined and mixed to prepare a chemical coating composition. Deionized water 99.30% by weight Fluorosilicate (25% by weight) 0.40% Tartaric acid 0.20% by weight Bismuth subnitrate; Bi5O(OH)9(NO3) 40.07% Glycoluryl resin 200 ppm Copper nitrate (1.841%Cu)0.05%

[0128] The pH of the mixture was 1.97. The pH was increased using a 10% ammonium bicarbonate solution (Bonderite® M-AD700) until a pH of 3.5 was achieved. This yielded a clear, slightly blue / green solution containing 506 ppm Bi, 10 ppm Cu, 200 ppm glycoluryl resin, 1000 ppm fluorosilicic acid, and 2000 ppm tartaric acid.

[0129] The solution was heated to 32°C. Using this bismuth conversion coating composition, an ACT CRS panel was dip-coated according to the coating process described above. This resulted in a visibly black coating on the CRS substrate containing the elements Bi, O, C, Cu, and Fe.

[0130] (Example 15) The following materials were combined and mixed to prepare a chemical coating composition. Deionized water 99.30% by weight Fluorosilicate (25% by weight) 0.40% Tartaric acid 0.20% by weight Bismuth subnitrate; Bi5O(OH)9(NO3) 40.07% Copper nitrate (1.841%Cu)0.05% Sodium nitrobenzenesulfonate (SNBS) 100 ppm

[0131] The pH of the mixture was 2.08. The pH was increased using a 10% ammonium bicarbonate solution (Vondelite® M-AD700) until a pH of 3.5 was achieved. This yielded a clear, slightly blue / green solution containing 506 ppm Bi, 100 ppm SNBS, 1000 ppm fluorosilicic acid, and 2000 ppm tartaric acid.

[0132] The solution was heated to 32°C. Using this bismuth conversion coating composition, ACT CRS panels were dip-coated according to the coating process described above. This resulted in a visibly black coating containing the elements Bi, O, C, Cu, and Fe.

[0133] (Example 16) In this example, different types of ACT metal panels (CRS, EG, HDG, and Al6111 panels) were coated and tested. The following materials were blended and mixed to prepare the chemical conversion coating compositions. Deionized water 99.28% by weight Bismuth subnitrate; Bi5O(OH)9(NO3) 40.07% Fluorosilicate (25% by weight) 0.40% Tartaric acid 0.20% by weight Copper nitrate (1.841%Cu) 0.05%

[0134] The pH of the mixture was 2.08. The pH was increased using a 10% ammonium bicarbonate solution (Vondelite® M-AD700) until a pH of 3.5 was achieved. This yielded a clear, slightly blue / green solution containing 506 ppm Bi, 10 ppm Cu, 1000 ppm fluorosilicic acid, and 2000 ppm tartaric acid. The mixture also contained undissolved bismuth subnitrate (white solid).

[0135] Following the application process described above, ACT CRS, EG, HDG, and Al6111 panels were dip-coated. This resulted in a visibly black coating on each of the different metal substrate samples. Each bismuth conversion coating contained the elements Bi, O, C, and Cu, along with the metals from their respective base substrates. After application of the bismuth conversion coating, the panels were coated with cathode electrodeposition coating, BASF Casoguard 800, without drying or stopping the process, according to the parameters described above for the bismuth conversion coating and E-coat process. Coating time = 4.0 minutes. For comparison, ACT panels coated with commercially available tricationic zinc phosphate (Bonderite® M-ZN958) were coated using the same zinc phosphate treatment process as those E-coated with BASF Casoguard 800 using the same coating parameters.

[0136] The appearance of the E-coat on the bismuth chemical conversion coated panel was smooth and uniform, with no mapping defects. The color of the cured paint on the bismuth chemical conversion coated panel was noticeably darker than that of the zinc phosphate coated control panel. The thickness of the dry E-coat was measured on the bismuth chemical conversion coating, which provided a thickness comparable to that of the zinc phosphate control panel.

[0137] [Table 1]

[0138] paint adhesion Paint adhesion was evaluated using GMW14829 / 14704. Procedure GMW14704 includes three separate tests: initial cross-hatching, cross-hatching following 24 hours of water immersion, and cross-hatching following 48 hours of water immersion. Each cross-hatching is followed by a tape pull as defined by General Motors' test method, with higher percentages indicating better performance. Three panels were tested. Different panels were used for the 24-hour and 48-hour immersion tests.

[0139] [Table 2]

[0140] The paint adhesion to the bismuth coating is comparable to that of the zinc phosphate control.

[0141] Corrosion performance The cyclic corrosion performance was evaluated using GMW14872, Exposure C (26 cycles, mass loss = 3.892 g). The test cycle was defined by General Motors' test method and included a series of exposures to humidity, water mist, and salt spray. Painted panels were scribed and subjected to 26 cycles. Panels were tested three times.

[0142] [Table 3]

[0143] Its corrosion resistance to bismuth coatings is comparable to that of zinc phosphate controls.

[0144] The coating weight and thickness of bismuth conversion coatings on several unpainted panels were characterized. The average bismuth conversion coating weight, measured as bismuth, was determined using Niton Xl3t (X-ray fluorescence), and the coating thickness was determined using glow discharge emission spectroscopy elemental depth (depth profiling).

[0145] [Table 4]

[0146] (Example 16') Modified washing The above Example 16 was repeated with a second set of ACT panels with the following process modification: a single “cleaning” step of spraying Bonderite® C-AK T51 for 90 seconds was replaced with the following two consecutive “cleaning” steps: 1) spraying Bonderite® C-AK T51 at 10 psi for 60 seconds, followed immediately by 2) immersion in Bonderite® C-AK T51 for 120 seconds. After bismuth conversion coating and rinsing, the properties of the bismuth conversion coating on some unpainted panels were evaluated. The average bismuth equivalent coating weight, measured as bismuth, was determined using Nitron Xl3t (X-ray fluorescence), and the coating thickness was determined using glow discharge emission spectroscopy elemental depth (depth profiling).

[0147] [Table 5]

[0148] The E-coat of the bismuth chemical conversion coated panel had a smooth and uniform appearance with no mapping defects. The color of the cured paint on the bismuth chemical conversion coated panel was noticeably darker than that of the zinc phosphate coated control panel. The thickness of the dry E-coat was measured on the bismuth chemical conversion coating, which provided a thickness comparable to that of the zinc phosphate control panel.

[0149] [Table 6]

[0150] Corrosion performance The panel of Example 16' was evaluated for cyclic corrosion performance using GMW14872, with exposure C corrected and used (29 cycles, mass loss = 4.065 g).

[0151] [Table 7]

[0152] The cyclic corrosion performance of the panels in Example 16' was evaluated using Ford L-467 under different testing methods. The test cycle was defined by Ford Motor Company's test methodology and included a series of exposures to humidity, water mist, and salt spray. Painted panels were scribed and tested for a period of 6 weeks. Panels were tested three times.

[0153] [Table 8]

[0154] (Example 17) Example 16 was repeated by reducing the amount of tartaric acid (from 0.20% by weight to 0.108% by weight). The pH of the mixture was 2.0. The pH was increased using a 10% ammonium bicarbonate solution (Vondelite® M-AD700) until a pH of 3.5 was achieved. This yielded a clear, slightly blue / green solution containing 506 ppm Bi, 10 ppm Cu, 1000 ppm fluorosilicic acid, and 1080 ppm tartaric acid. The solution was clear and contained no undissolved (visible) solids.

[0155] Following the procedure of Example 16, ACT CRS, EG, HDG, and Al6111 panels with visibly black coatings were obtained on different metal substrate samples, respectively. Each bismuth conversion coating contained the elements Bi, O, C, and Cu, along with metals from their respective base substrates. The E-coat had a smooth and uniform appearance with no mapping defects. The color of the cured paint on the bismuth conversion coated panels was visibly darker than that of the zinc phosphate coated control panels. The E-coat dry film thickness was comparable between the bismuth coating and the zinc phosphate coated control. Zero immersion and 48-hour immersion paint adhesion and corrosion resistance tests were performed according to the procedure of Example 16, and the results are shown in the table below.

[0156] [Table 9]

[0157] The paint adhesion to bismuth coatings is comparable to that of zinc phosphate controls, except for EG and HDG substrates.

[0158] [Table 10]

[0159] The corrosion resistance of the bismuth coating is comparable to that of the zinc phosphate control.

[0160] (Example 18) Example 16 was repeated by increasing the amount of tartaric acid (from 0.20% by weight to 0.54% by weight). The pH of the mixture was 2.0. The pH was raised using a 10% ammonium bicarbonate solution (Vondelite® M-AD700) until a pH of 3.5 was achieved. This yielded a clear, slightly blue / green solution containing 506 ppm Bi, 10 ppm Cu, 1000 ppm fluorosilicic acid, and 5400 ppm tartaric acid. The solution was clear and contained no undissolved (visible) solids.

[0161] Following the procedure of Example 16, ACT CRS, EG, HDG, and Al6111 panels with visibly black coatings were obtained on different metal substrate samples, respectively. Each bismuth conversion coating contained the elements Bi, O, C, and Cu, along with metals from their respective base substrates. The bismuth conversion coatings on CRS substrates were examined using field emission scanning electron microscopy (FESEM) at a maximum magnification of 100,000x. The bismuth conversion coatings deposited on CRS showed a complete substrate coating layer with a uniform nodular structure. No exposed CRS substrate was observed. The appearance of the E-coat was smooth and uniform, with no mapping defects. The color of the cured paint on the bismuth conversion coated panels was visibly darker than that of the zinc phosphate coated control panel. The E-coat dry film thickness was comparable between the bismuth coating and the zinc phosphate coated control. Zero immersion and 48-hour immersion paint adhesion and corrosion resistance tests were performed according to the procedure of Example 16, and the results are shown in the table below.

[0162] [Table 11]

[0163] The paint adhesion on bismuth coatings is comparable to that of zinc phosphate controls, except for EG substrates.

[0164] [Table 12]

[0165] The corrosion resistance of the bismuth coating is comparable to that of the zinc phosphate control.

[0166] (Example 19) Example 16 was repeated using 0.10 wt% sodium gluconate instead of 0.20 wt% tartaric acid to obtain a mixture with pH=2.0. The pH was increased using a 10% ammonium bicarbonate solution (Vondelite® M-AD700) until pH=3.5 was achieved. This yielded a clear, slightly blue / green solution containing 506 ppm Bi, 10 ppm Cu, 1000 ppm fluorosilicic acid, and 1000 ppm sodium gluconate. The solution was clear and contained no undissolved (visible) solids.

[0167] Following the procedure of Example 16, ACT CRS, EG, HDG, and Al6111 panels were obtained, each with a visibly black coating on different metal substrate samples. Each bismuth conversion coating contained the elements Bi, O, C, and Cu, along with the metal from the respective base substrate.

[0168] (Example 20) The following materials were combined and mixed to prepare a chemical coating composition. Deionized water 99.30% by weight Fluorosilicate (25% by weight) 0.40% Tartaric acid 0.20% by weight Bismuth subnitrate; Bi5O(OH)9(NO3) 40.07% Polyamide amine resin 0.005%

[0169] The polyamidoamine polymer additive is Versamide 150, commercially available from Gabriel Performance Products, which is a reaction product of dimerized fatty acids and polyamines, and is described as having a MW of 200-10,000 daltons and an amine content of 100-1000 mg KOH per gram of resin.

[0170] The pH of the mixture was 2.0. The pH was increased using a 10% ammonium bicarbonate solution (Bonderite® M-AD700) until a pH of 3.5 was achieved. This yielded a slightly yellow solution containing 506 ppm Bi, 50 ppm polyamideamine resin, 1000 ppm fluorosilicic acid, and 2000 ppm tartaric acid. The solution was clear and contained no undissolved (visible) solids.

[0171] The solution was heated to 32°C. ACT CRS, EG, HDG, and Al6111 panels were dip-coated according to the application process described above. This resulted in a visibly black coating on each of the different metal substrate samples. Each bismuth conversion coating contained the elements Bi, O, and C, along with the metal from their respective base substrates.

[0172] (Example 21) Instead of 0.005% polyamidoamine resin, Example 20 was repeated using a resin based on phenalkamine resin, cashew nut shell liquid (cardanol, cardol, anacardic acid), and polyamine, commercially available from Caldrite under the trade name Caldrite NX-8101, with MW:=200-2,000 Daltons; amine content: 100-500 mg KOH per gram of resin, to obtain a pH=2.0 mixture. The pH was increased using a 10% ammonium bicarbonate solution (Bonderite® M-AD700) until pH=3.5 was achieved. This yielded a slightly yellow solution containing 506 ppm Bi, 50 ppm phenalkamine resin, 1000 ppm fluorosilicic acid, and 2000 ppm tartaric acid. The solution was clear and contained no undissolved (visible) solids.

[0173] The solution was heated to 32°C. Following the application process described above, ACT CRS, EG, HDG, and Al6111 panels were dip-coated. This resulted in a visibly black coating on each of the different metal substrate samples. Each bismuth conversion coating contained the elements Bi, O, and C, along with the metal from their respective base substrates.

[0174] (Example 22) Example 16 was repeated by adding 0.025% of Rudox TMA, a commercially available aqueous dispersion of 20% colloidal silica from Grace Material Technologies, to obtain a mixture with a pH of 2.0. The pH was increased using a 10% ammonium bicarbonate solution (Vondelite® M-AD700) until a pH of 3.5 was achieved. This yielded a clear, slightly blue / green solution containing 506 ppm Bi, 10 ppm Cu, 50 ppm SiO2, 1000 ppm fluorosilicic acid, and 2000 ppm tartaric acid. The solution was clear and contained no undissolved (visible) solids.

[0175] The solution was heated to 32°C. ACT CRS, EG, HDG, and Al6111 panels were dip-coated according to the application process described above. This resulted in a visibly black coating on each of the different metal substrate samples. Each bismuth conversion coating contained not only the metal from its respective base substrate, but also the elements Bi, O, C, Si, and Cu.

[0176] Post-treatment after bismuth conversion coating (Example 23) Zirconium-containing post-treatment In this embodiment, ACT CRS, EG, HDG, and Al6111 panels having a bismuth conversion coating were subjected to a zirconium-containing post-treatment, and their compatibility with the bismuth conversion coating layer was evaluated.

[0177] Following the application process described above, the bismuth conversion coating composition of Example 16 was used to dip-coat ACT CRS, EG, HDG, and Al6111 panels, after which a zirconium-containing post-treatment was spray-deposited according to the following process.

[0178] Bismuth conversion coating / post-treatment process Cleaning solution: Bonderite® C-AK T51 (2% v / v, 49℃, FAlK 5.0, 90-second spray, 10 psi) Rinse solution: Tap water (38°C, spray for 60 seconds, 10 psi) Rinse solution: Deionized water (21°C, 60-second spray, 10 psi) Chemical coating: Immerse at 32°C for 120 seconds. Rinse solution: Deionized water (21°C, 60-second spray, 10 psi) Post-treatment: Bonderite® M-PT54NC, acidic, chromium-free, zirconium-containing passivation post-treatment (0.5% v / v, 21°C, pH=4.0, 60-second spray) Rinse solution: Deionized water (24°C, 60-second spray, 10 psi) Air drying (ambient temperature, compressed air, 90 psi)

[0179] Visibly black coatings were deposited on each of the ACT CRS, EG, HDG, and Al6111 metal substrate samples. Each bismuth conversion coating contained the elements Bi, O, C, and Cu, as well as metals from the respective base substrates. The bismuth conversion coatings were not significantly removed by reaction with the zirconium-containing post-treatment composition, indicating that acidic post-treatment can be performed after the bismuth conversion coating.

[0180] (Example 24) Organic polymer sealant The coating process of Example 23 was repeated using an organic polymer sealant instead of a zirconium-containing post-treatment. To evaluate compatibility with the bismuth conversion coating layer, the organic polymer sealant was applied to ACT CRS, EG, HDG, and Al6111 panels having a bismuth conversion coating.

[0181] ACT CRS, EG, HDG, and Al6111 panels were dip-coated using a bismuth conversion coating composition according to the application process of Example 23, and subsequently spray-deposited 0.75% v / v Bonderite® M-PT99X, an organic polymer sealant, using the following parameters: 21°C, pH=4.0, spray for 60 seconds.

[0182] Visibly black coatings were deposited on each of the ACT CRS, EG, HDG, and Al6111 metal substrate samples. Each bismuth conversion coating contained the elements Bi, O, C, and Cu, along with metals from the respective base substrates. The bismuth conversion coatings were not significantly removed by contact / reaction with the organic polymer sealant composition, indicating that bismuth conversion coatings may be suitable for organic polymer sealing when necessary.

[0183] (Example 24') Organic polymer sealant Example 24 above was repeated with a second set of the ACT panel above, with the following process modifications: a single "cleaning" step of spraying Bonderite® C-AK T51 for 90 seconds was replaced with the following two consecutive "cleaning" steps: 1) spraying Bonderite® C-AK T51 at 10 psi for 60 seconds, then immediately 2) immersing in Bonderite® C-AK T51 for 120 seconds, and replacing "air drying" with "E-coat: BASF Casoguard 800 (35°C, 270-second immersion, 0.9 Amps constant current ~230V), rinse solution: deionized water (24°C, 60-second spray, 10 psi), and paint curing: oven baking (185°C, 35 minutes).

[0184] ACT CRS, EG, HDG, and Al6111 panels were dip-coated as described above. This resulted in a visibly black coating on each of the different metal substrate samples. Each bismuth conversion coating contained the elements Bi, O, C, and Cu, along with metals from the respective base substrates. To evaluate corrosion performance, the panels were coated with cathode electrodeposition coating, BASF Casoguard 800, without drying or stopping the process, according to the parameters described above for the bismuth conversion coating, E-coat process. Coating time = 4.5 minutes.

[0185] The E-coat of the bismuth chemical conversion coated panel had a smooth and uniform appearance with no mapping defects. The color of the cured paint on the bismuth chemical conversion coated panel was noticeably darker than that of the zinc phosphate coated control panel. The dry E-coat thickness was measured on the bismuth chemical conversion coating, which provided a thickness comparable to that of the zinc phosphate control panel.

[0186] [Table 13]

[0187] Corrosion performance The panel of Example 24' was evaluated for cyclic corrosion performance using GMW14872, with exposure C corrected and used (29 cycles, mass loss = 4.065 g).

[0188] [Table 14]

[0189] Using a different test, the cyclic corrosion performance of the panels in Example 24' was evaluated using Ford, L-467. The test cycle was defined by Ford Motor Company's test methodology and included a series of exposures to humidity, water mist, and salt spray. Painted panels were scribed and tested for a period of 6 weeks. Panels were tested three times.

[0190] [Table 15]

[0191] The invention described herein is explained in accordance with relevant legal standards, and therefore the description is illustrative rather than restrictive. Variations and modifications to the disclosed embodiments may be obvious to those skilled in the art and fall within the scope of the invention. Accordingly, the scope of legal protection granted to the invention can only be determined by considering the following claims.

Claims

1. A) Dissolve and / or disperse bismuth, B) At least one water-soluble organic chelating agent present in an amount sufficient to solubilize or disperse A), C) Dissolved copper ions, Includes, An acidic aqueous bismuth chemical coating composition having a pH in the range of approximately 2.0 to approximately 6.

2. The acidic aqueous bismuth chemical coating composition according to claim 1, wherein A) comprises at least one dissolved Bi(III) and a dissolved and / or dispersed bismuth compound, and B) comprises one or more water-soluble organic acids and salts thereof.

3. The acidic aqueous bismuth chemical coating composition according to claim 1, wherein the one or more water-soluble organic acids and salts thereof are selected from aliphatic or aromatic; linear, branched or cyclic; saturated or unsaturated C3-C12 organic acids and salts thereof.

4. The acidic aqueous bismuth chemical coating composition according to claim 2, wherein the one or more water-soluble organic acids and salts thereof comprise at least one organic polycarboxylic acid and a salt thereof.

5. The acidic aqueous bismuth chemical coating composition according to claim 4, wherein the at least one organic polycarboxylic acid and its salt comprises a substituted and / or unsubstituted alpha,omega-dicarboxylic acid.

6. The acidic aqueous bismuth chemical coating composition according to claim 5, wherein the substituted and / or unsubstituted alpha,omega-dicarboxylic acids and their salts comprise one or more substituted and / or unsubstituted propanediic acid, butanediic acid, pentanediic acid, hexanediic acid, heptanediic acid, octanedic acid, nonanediic acid, decanediic acid and their salts.

7. The acidic aqueous bismuth chemical coating composition according to claim 2, wherein the one or more water-soluble organic carboxylic acids and their salts include tartaric acid and its salts.

8. The acidic aqueous bismuth chemical coating composition according to claim 1, comprising less than 1% by weight of a phosphorus-containing acid and / or a salt thereof, and less than 1% by weight of nickel.

9. The acidic aqueous bismuth conversion coating composition according to claim 1, comprising one or more additional components selected from the group consisting of free fluorides, nitrates, and sources of Si-based substances.

10. The acidic aqueous bismuth chemical coating composition according to claim 1, wherein the acidic aqueous bismuth chemical coating composition comprises at least one pH adjusting agent and has a pH of about 2.5 to about 5.

0.

11. The acidic aqueous bismuth conversion coating composition according to claim 1, wherein the dissolved and / or dispersed bismuth is present at a total concentration of about 5 to 10,000 ppm.

12. The acidic aqueous bismuth chemical coating composition according to claim 1, wherein the dissolved and / or dispersed bismuth comprises one or more of bismuth nitrates, oxides, and hydroxides.

13. The acidic aqueous bismuth chemical coating composition according to claim 1, wherein the dissolved and / or dispersed bismuth is selected from bismuth nitrate, bismuth nitrate pentahydrate, bismuth nitrite, bismuth oxide, bismuth hydroxide, and combinations thereof.

14. The acidic aqueous bismuth conversion coating composition according to claim 1, wherein the at least one water-soluble organic chelating agent is present in a total concentration of about 50 to 100,000 ppm.

15. A replenishment composition comprising a storage stabilization composition containing bismuth, copper, nitric acid, and optionally nitrate ions, for replenishing the acidic aqueous bismuth chemical coating composition described in claim 1 after use.

16. a) A step of contacting the metal surface of a substrate preferably selected from an iron metal, a zinc-containing metal, and an aluminum-containing metal with the acidic aqueous bismuth conversion coating composition according to claim 1 for a time sufficient to form a bismuth conversion coating layer on at least a portion of the metal surface, b) A step of rinsing the bismuth chemical coating layer with a rinse solution containing water, A method for depositing a bismuth conversion coating on a substrate having a metal surface, including the above.

17. A method for depositing a bismuth conversion coating according to claim 16, further comprising step c) of subjecting at least a portion of a metal surface having a bismuth conversion coating layer to post-treatment and / or sealing rinse before painting.

18. The method according to claim 16 or 17, comprising the step of coating at least a portion of a metal surface having a bismuth conversion coating layer with a cathode-depositable electrophoretic dip coating, wherein the metal surface is not dried after rinsing step b) and before being coated with the cathode-depositable electrophoretic dip coating.

19. A substrate having a metal surface including a bismuth conversion coating layer deposited thereon, wherein the bismuth conversion coating layer includes bismuth oxide and / or bismuth hydroxide, and further includes at least one of the elements Cu, Cu(I) and Cu(II).

20. A) Dissolve and / or disperse bismuth, B) A complex fluoroacid present in an amount sufficient to solubilize or disperse A), preferably a fluorosilicic acid. C) Dissolved copper ions, and At least one pH adjuster in the form of an acid, a base, or a buffered acid / base combination, present in the composition in an amount sufficient to provide a pH in the range of about 2.0 to 6.

0. An acidic aqueous bismuth chemical coating composition containing the above.

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