Bismuth compositions for metal pretreatment applications

Abstract

The present invention provides a bismuth conversion coating composition for depositing a bismuth conversion coating on a variety of metal substrates, a method for preparing the bismuth conversion coating composition, a method for depositing a bismuth conversion coating on a metal substrate, and an article having a metal surface comprising the bismuth conversion coating.

Description

Field of the Invention

[0001] The present invention relates to bismuth compositions, such as conversion coating compositions for metal pretreatment applications, such as deposited on metal surfaces to improve corrosion resistance and / or paint adhesion, methods of preparing such compositions, methods of coating metal substrates, and articles having a metal surface coated with such compositions. Background Art

[0002] Many consumer and industrial products are formed from metal substrates and are exposed to harsh weather. As a result, these metal articles are subject to corrosive environments; thus, they are typically coated with protective coatings, including anti-corrosion coatings and paints. Many such anti-corrosion coatings are referred to as conversion coatings, which in the art are understood to be coatings formed by contacting a metal surface with a reactive coating composition to form a conversion coating thereon. While these conversion coatings enhance the corrosion resistance of the metal, further improvement of the conversion coatings is an ongoing market need for automotive and large household appliance applications.

[0003] Typical methods of applying a conversion coating to a metal substrate include the steps of cleaning, rinsing, depositing the conversion coating, and optionally post-rinsing and / or sealing. The metal substrate that is at least partially coated with the conversion coating is then most often subjected to a painting step (such as by electrophoretic coating, also known as E-coating).

[0004] Traditional tri-cationic zinc phosphate conversion coating systems provide excellent corrosion resistance and paint adhesion, but contain undesirable heavy metals and generate environmentally harmful waste by the precipitation of heavy metal phosphate sludge. Like the spills in a zinc phosphate bath, these sludges contain high concentrations of phosphate ions, both of which can cause eutrophication of natural water sources. Zinc phosphate baths also operate at high temperatures, which requires increased energy use. Thus, it is desirable to reduce or avoid the disadvantages of the zinc phosphate process while still achieving comparable corrosion resistance and paint adhesion. Zirconium-based conversion coatings have been proposed as an alternative to tri-cationic zinc phosphate, but in some uses, these conversion coatings do not meet industrial requirements, particularly those of the automotive industry.

[0005] Accordingly, there is a great need to develop alternative conversion coatings and methods. Summary of the Invention

[0007] Bismuth conversion coating compositions for depositing bismuth conversion coatings on metal substrates have been developed. Metal substrates pretreated with an aqueous bismuth conversion coating composition and then painted, particularly E-coated paint, exhibit improved to equivalent corrosion resistance and paint adhesion compared to tri-cationic zinc phosphate controls.

[0008] A bismuth conversion coating composition can be applied to a substrate metal surface by immersing (submerging) the metal substrate in an aqueous solution or spraying the solution onto the metal substrate. Alternatively, the coating composition can be applied by roll coating or other known conversion coating deposition methods.

[0009] Preferred embodiments of the bismuth conversion coating composition provide a bismuth conversion coating having corrosion resistance and paint adhesion properties comparable to those of conventional tri-cationic zinc phosphate compositions and provide improvements in reducing environmental impact for the following reasons: no heavy metals such as Zn, Ni, and Mn are added; there is no phosphorus, and the operating temperature is reduced.

[0010] Some uses of the bismuth conversion coating composition include coating the surfaces of metal substrates such as ferrous, zinc-containing, aluminum-containing surfaces and combinations thereof, which surfaces will subsequently be painted and require paint adhesion and corrosion resistance. Suitable applications may include transportation, such as automotive OEM (body-in-white), automotive components; the energy industry, such as wind and solar energy equipment; agricultural and construction equipment; recreational vehicles; building components; household items such as appliances; office furniture; metal coils; metal containers, etc.

[0011] According to one aspect of the present invention ("Aspect 1"), there is provided a conversion coating composition comprising, consisting essentially of, or consisting of an acidic aqueous bismuth conversion coating composition, the acidic aqueous bismuth conversion coating composition comprising:

[0012] A) dissolved and / or dispersed bismuth;

[0013] B) at least one water-soluble organic chelating agent present in an amount sufficient to dissolve or disperse A);

[0014] C) dissolved copper ions; and

[0015] having a pH in the range of about 2.0 to about 6.

[0016] Aspect 2: The acidic aqueous bismuth conversion coating composition according to Aspect 1, wherein A) comprises at least one of dissolved Bi(III) and dissolved and / or dispersed bismuth compounds; B) comprises one or more water-soluble organic acids and their salts.

[0017] Aspect 3: The acidic aqueous bismuth conversion coating composition according to Aspect 2, wherein the one or more water-soluble organic acids and their salts are selected from aliphatic or aromatic; linear, branched or cyclic; saturated or unsaturated C3-C12 organic acids and their salts.

[0018] Aspect 4: The acidic aqueous bismuth conversion coating composition as described in Aspect 2, wherein the one or more water-soluble organic acids and their salts include at least one organic polycarboxylic acid and its salts.

[0019] Aspect 5: The acidic aqueous bismuth conversion coating composition as described in Aspect 4, wherein the at least one organic polycarboxylic acid and its salts include substituted and / or unsubstituted α,ω-dicarboxylic acids.

[0020] Aspect 6: The acidic aqueous bismuth conversion coating composition as described in Aspect 5, wherein the substituted and / or unsubstituted α,ω-dicarboxylic acids and their salts include one or more of substituted and / or unsubstituted malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid and their salts.

[0021] Aspect 7: The acidic aqueous bismuth conversion coating composition as described in Aspect 2, wherein the one or more water-soluble organic carboxylic acids and their salts include tartaric acid and its salts.

[0022] Aspect 8: The acidic aqueous bismuth conversion coating composition as described in Aspect 1, which contains less than 1 wt% of phosphoric acid and / or its salts and less than 1 wt% of nickel.

[0023] Aspect 9: The acidic aqueous bismuth conversion coating composition as described in Aspect 1, which contains one or more additional components selected from sources of free fluoride ions, nitrate ions and Si-based substances.

[0024] Aspect 10: The acidic aqueous bismuth conversion coating composition as described in Aspect 1, wherein the acidic aqueous bismuth conversion coating composition contains at least one pH regulator and has a pH of about 2.5 to about 5.0.

[0025] Aspect 11: The acidic aqueous bismuth conversion coating composition as described in Aspect 1, wherein the dissolved and / or dispersed bismuth is present at a total concentration of about 5 to 10,000 ppm.

[0026] Aspect 12: The acidic aqueous bismuth conversion coating composition as described in Aspect 1, wherein the dissolved and / or dispersed bismuth includes one or more of bismuth nitrate, bismuth oxide and bismuth hydroxide.

[0027] Aspect 13: The acidic aqueous bismuth conversion coating composition as described in Aspect 1, wherein the dissolved and / or dispersed bismuth is selected from bismuth nitrate; bismuth nitrate pentahydrate; bismuthyl nitrate; bismuth oxide; bismuth hydroxide and combinations thereof.

[0028] Aspect 14: The acidic aqueous bismuth conversion coating composition as described in Aspect 1, wherein the at least one water-soluble organic chelating agent is present at a total concentration of about 50 to 100,000 ppm.

[0029] Another aspect of the present invention (Aspect 15) comprises the following, consists essentially of the following, or consists of the following: a supplement composition for replenishing the acidic aqueous bismuth conversion coating composition as described above after use, the supplement composition comprising a storage-stable composition containing bismuth, copper, nitric acid, and optionally nitrate.

[0030] Another aspect of the present invention (Aspect 16) comprises the following, consists essentially of the following, or consists of the following: a method for depositing a bismuth conversion coating on a substrate having a metal surface, the method comprising the steps of:

[0031] a. contacting the metal surface of the substrate with the acidic aqueous bismuth conversion coating composition as described above for a time sufficient to form a bismuth conversion coating on at least a portion of the metal surface, the metal surface of the substrate preferably selected from ferrous metals, zinc-containing metals, and aluminum-containing metals; and

[0032] b. rinsing the bismuth conversion coating with a rinsing agent comprising water.

[0033] Aspect 17: The method for depositing a bismuth conversion coating of Aspect 16, which further comprises the step c) of coating at least a portion of the metal surface having the bismuth conversion coating by cathodic electrodeposition dip coating, and wherein the metal surface is not dried after the rinsing step b) and before coating by cathodic electrodeposition dip coating.

[0034] Another aspect of the present invention (Aspect 18) comprises the following, consists essentially of the following, or consists of the following: a substrate having a metal surface with a bismuth conversion coating deposited thereon, wherein the bismuth conversion coating comprises bismuth oxide and / or bismuth hydroxide, and further comprises at least one of the elements Cu, Cu(I), and Cu(II).

[0035] According to yet another aspect of the present invention (Aspect 19), there is provided a conversion coating composition comprising the following, consisting essentially of the following, or consisting of the following: an acidic aqueous bismuth conversion coating composition, the acidic aqueous bismuth conversion coating composition comprising:

[0036] A) dissolved and / or dispersed bismuth;

[0037] B) a complex fluoroacid, preferably fluorosilicic acid, present in an amount sufficient to dissolve or disperse A);

[0038] C) dissolved copper ions; and

[0039] at least one pH regulator 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 about 2.0 to 6.0.

[0040] Unless otherwise specified, any combination or sub - combination of the foregoing aspects is considered to fall within the scope of the present invention.

[0041] For a variety of reasons, the aqueous bismuth conversion coating compositions according to the present invention and as defined above may be substantially free of many of the ingredients used in compositions for similar purposes in the prior art. Specifically, for each of the ingredients preferably minimized as listed below, independently and in the given order of increasing preference, when in direct contact with a metal in a method according to the present invention, the aqueous composition according to the present invention contains no more than 1.0, 0.5, 0.35, 0.10, 0.08, 0.04, 0.02, 0.01, 0.001 or 0.0002% (the values are more preferably in grams per liter and most preferably the values are in ppm) of the following various ingredients: zinc, nickel, cobalt, manganese, chromium, cyanide, nitrite ions, organic surfactants, formaldehyde, formamide, urea, hydroxylamine, ammonia, tertiary amines, cyclic amines such as hexamethylenetetramine; silicates, siloxanes, organosiloxanes, silanes; lanthanide metals, rare earth metals; containing phosphoric acid and / or its salts; sulfur, such as sulfates, sulfonic acids; permanganates; perchlorates; boron, such as borax, borates; strontium; and / or free chloride ions.

[0042] In addition, for each of the ingredients preferably minimized as listed below, independently and in the given order of increasing preference, the freshly deposited bismuth conversion coating and the freshly deposited post - treatment agent according to the present invention contain no more than 1.0, 0.5, 0.35, 0.10, 0.08, 0.04, 0.02, 0.01, 0.001 or 0.0002% (the values are more preferably in parts per thousand (ppt)) of the following various ingredients: chromium, cyanide, nitrite ions, organic surfactants, formaldehyde, formamide, urea, hydroxylamine, ammonia and hexamethylenetetramine; silicates, siloxanes, organosiloxanes, silanes; rare earth metals; containing phosphoric acid and / or its salts; sulfur, such as sulfates, sulfonic acids; permanganates; perchlorates; boron, such as borax, borates; strontium; and / or chlorides.

[0043] Some materials may be present in the bismuth conversion coating working bath, for reasons such as carry - in from previous method steps, elution from the substrate, inclusion as counter - ions or contaminants. Non - limiting examples of materials that may be present and that it is desirable to minimize and that are not intentionally added to the bath include phosphates and silicates carried in from cleaners; free chloride ions may be present due to water contamination, while Fe, Zn and Al ions may be eluted from the substrate. Counter - ions that may be present include ammonia or ammonium ions, alkali metals (NH 4+ 、Na + 、K + ), sulfate, etc.

[0044] Unless the context clearly dictates otherwise or necessarily implies otherwise, the term "paint" includes all similar materials that can be designated by more specific terms, such as lacquer, enamel, varnish, shellac, topcoat, etc. Those skilled in the art will understand that the simple terms "metal" or "metallic" refer to materials composed of atoms of metallic elements such as iron, zinc, etc., whether articles or surfaces; in order of increasing preference in a given order, the total amount of metallic elements present is at least 55, 65, 75, 85 or 90 atomic %, and the simple term "iron-containing" includes pure iron and its alloys, such as steel, and likewise "zinc-containing" and "aluminum-containing" include pure metals and their respective alloys.

[0045] Except in the operating examples, or where otherwise indicated, all numbers expressing amounts of ingredients, reaction conditions, or defining compositional parameters used herein should be understood to be modified in all instances by the term "about". Throughout the specification, unless expressly stated to the contrary: percentages, "parts", and ratios are by weight or mass; the description of a group or class of materials as suitable or preferred for a given purpose in connection with the present invention implies that a mixture of any two or more members of that group or class is equally suitable or preferred; a component described in chemical terms refers to the component when added to any combination specified in the specification or when in situ generated by (one or more) chemical reactions between one or more newly added components and one or more components already present in the composition (when other components are added); the specification of a component as being in ionic form additionally implies the presence of sufficient counterions such that the composition as a whole and any substances added to the composition are electrically neutral; any counterions thus implicitly specified are preferably selected, to the extent possible, from other components specifically specified as being in ionic form; these counterions may be freely chosen except for those that would be detrimental to the purposes of the present invention; the molecular weight (MW) is the weight-average molecular weight; the term "mole" refers to "gram-mole", and the term itself and all its grammatical variants can be used for any chemical species defined by the type and number of all atoms present therein having a well-defined molecule, whether the species is ionic, neutral, unstable, hypothetical, or actually stable neutral substance; the term "storage-stable" should be understood to include solutions and dispersions that show no visually detectable tendency to phase separate during an observation period of at least 100 hours or preferably at least 1000 hours, during which the material is not disturbed mechanically and the temperature of the material is maintained at ambient room temperature (18 to 25 °C).

[0046] Organic materials will be understood to describe molecules composed of at least one carbon atom and (one or more) hydrogens bonded thereto, where the carbon may form chain or cyclic structures and may optionally include additional atoms and functional groups attached thereto (such as oxygen, silicon, phosphorus, and nitrogen).

[0047] These and other features and advantages of the present invention will become more apparent to those skilled in the art from a detailed description of the preferred embodiments. Detailed Description of the Invention

[0048] The present invention provides a bismuth conversion coating composition that can be used to coat the surface of a metal substrate. The aqueous acidic bismuth conversion coating composition comprises the following, or in some cases consists essentially of the following, or in some cases consists of the following:

[0049] A) dissolved and / or dispersed bismuth, desirably including Bi(III) ions, and optionally present dissolved and / or dispersed bismuth compounds;

[0050] B) at least one water-soluble organic chelating agent, desirably comprising one or more water-soluble organic acids capable of chelating the dissolved and / or dispersed bismuth, preferably increasing its solubility; and may have a pH in the range of about 2.0 to about 6.

[0051] C) copper(II) ions;

[0052] D) at least one metal etchant, desirably comprising a source of free fluoride ions, such as a fluoride ion-containing compound, such as HF and / or a complex fluoroacid that can provide a reservoir of free fluoride ions. The free and complex fluoride ions serve to increase the etching of the metal substrate surface;

[0053] E) at least one pH regulator in the form of an acid, base, or buffer acid / base combination for adjusting the pH to a range of 2 - 6, 2.5 - 5, 2.75 - 4.5, 3 - 4;

[0054] Optional components of the bismuth conversion coating composition include:

[0055] F) nitrate ions; and

[0056] G) Group IVB metals: Zr, Ti, Hf;

[0057] H) at least one accelerator; and

[0058] I) at least one water-soluble and / or water-dispersible polymeric compound.

[0059] The aqueous mixture can be in the form of a solution or a 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 the aqueous medium and mixtures in which one or more components of the mixture are partially dissolved in the aqueous medium.

[0060] Component A), i.e., dissolved and / or dispersed bismuth, desirably includes dissolved Bi(III), but can be derived from dissolved metallic bismuth, dissolved and / or dispersed bismuth compounds, or can be derived from Bi(V) desirably having a reducing agent available for reducing the oxidation state of bismuth to Bi(III). Some sources of bismuth may be relatively insoluble in water and can be used in the present invention by first dissolving in acid or by adjusting the pH of the conversion coating composition. Illustrative, non-limiting examples of bismuth sources include bismuth compounds such as bismuth nitrate Bi(NO3)3; bismuth nitrate pentahydrate Bi(NO3)3·5H2O; bismuthyl 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); bismuth subcitrate C 12 H8BiK5O 14 ; sodium bismuth tartrate (C4H4O6)2BiNa; sodium nitrilotriacetate bismuth C 24 H 28 BiN4Na7O 25 , the complex sodium salt of nitrilotriacetic acid bismuth; bismuth subacetate CH3COOBiO; bismuth subcarbonate (basic bismuth carbonate) (BiO)2CO3; bismuth carbonate Bi2(CO3)3; bismuth fluoride BiF3; bismuth molybdate Bi2(MoO4)3; bismuth subsalicylate HOC6H4COOBiO(1:1 or 3:1); bismuth sulfate Bi2(SO4)3; bismuth silicate Bi4Si3O 12 ; complex silicate; bismuth hydroxide Bi(OH)3; bismuth tungstate Bi2(WO4)3; bismuth vanadate BiVO4. Illustrative, non-limiting examples of preferred bismuth sources include various Bi compounds: bismuth oxide, bismuth sulfate, bismuth nitrate, bismuthyl nitrate, and similarly at least partially water-soluble and / or acid-soluble bismuth materials.

[0061] Other Bi sources can be used, but they tend to be undesirable due to their counterions, environmental impact, and / or safety reasons. Other Bi sources such as: bismuth(V) phosphate Bi3(PO4)5; bismuth(III) orthophosphate BiPO4; bismuth halides, such as bismuth bromide BiBr3; BiOBr; bismuth oxybromide BiOBr; bismuth pentafluoride BiF5; bismuth trihydride BiH3; bismuth chloride BiCl3; bismuth oxychloride BiOCl; bismuth iodide BiI3; bismuth oxyiodide BiOI; also insoluble sodium bismuthate NaBiO3; bismuth oxalate Bi(C2O4)3; bismuth oleate [CH3(CH2)7CH=CH(CH2)7COO]3Bi; and gas releasing agents, such as bismuth butylthiolaureate CH 39(CH2)9CH(SC4H9)COOBi(OH)2 and bismuth sulfide Bi2S3, which release H2S gas when dissolved in acid.

[0062] Any inorganic or organic Bi(III) source can be used in the working bath, which provides Bi(III) that can be deposited as a conversion coating on a metal substrate, as disclosed herein, and does not negatively affect the objectives and benefits of the present invention. Combinations of two or more different bismuth compounds can be used.

[0063] The bismuth conversion coating composition useful in the present invention can have, for example, a concentration of component A), i.e., dissolved and / or dispersed bismuth, of about 5 to 10,000 ppm, 15 to 5000 ppm, 25 to 4000 ppm, 50 to 3000 ppm, 75 to 2000 ppm, 90 to 1500 ppm, 100 to 1000 ppm, 200 to 750 ppm, or 250 to 600 ppm. According to an advantageous embodiment of the present invention, the bismuth compound preferably used as the Bi(III) source is water-soluble. For example, the bismuth compound can have a solubility of at least 0.5 wt%, at least 1 wt%, at least 5 wt%, or at least 10 wt% in water at 25°C. However, in other embodiments, the bismuth compound can be dispersed in water, preferably providing a storage-stable dispersion that provides Bi(III) ions together with component B) in the bismuth conversion coating composition and / or bath.

[0064] Component B), i.e., at least one water-soluble organic chelating agent, preferably comprises one or more water-soluble organic acids and / or their salts capable of chelating the dissolved and / or dispersed bismuth, preferably substituted and / or unsubstituted organic carboxylic acids. In one embodiment, Component B) comprises water-soluble C3-C12, preferably C4-C9 organic acids and / or their salts. (Meth)acrylic monomeric acids and their salts are preferably avoided as they tend to polymerize in the bath. The organic acid can be aliphatic or aromatic; linear, branched or cyclic; saturated or unsaturated and can include one or more nitrogen-containing functional groups. The water-soluble organic acid can be a monocarboxylic acid, but desirably can be a di-, tri-, tetra-carboxylic acid (organic polycarboxylic acid) or even have a greater number of carboxyl groups, provided that they do not interfere with the object of the present invention. Having multiple carboxyl groups provides multiple donor atoms available for binding metal atoms. In a preferred embodiment, the organic polycarboxylic acid is at least bidentate, meaning that it has two donor atoms allowing it to bind to the central bismuth atom or ion at two positions. Providing a bidentate donor is entropically favorable compared to two separate donors such as monocarboxylic acids like formic acid. The water-soluble organic acid and / or its salt can be substituted with other functional groups such as hydroxyl groups. In one embodiment, the organic carboxylic acid can be a hydroxy-functionalized polycarboxylic acid. In a further embodiment, the hydroxy-functionalized polycarboxylic acid can desirably have a ratio of OH groups to COOH groups of about 0.5:1 to 5:1. Desirably, Component B) is present in an amount sufficient to dissolve or suspend Bi ions, such as 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 7,500 ppm, 450 to 5,000 ppm or 500 to 3,000 ppm.

[0065] Non-limiting examples of suitable materials for Component B) can include: organic acids having multiple carboxylic acid functional groups, such as α,ω-dicarboxylic acids, e.g., malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, etc., which can also include one or more additional functional groups, such as hydroxy-functional groups, along the carbon chain. Specific examples of materials suitable for Component B) include tartaric acid, citric acid, ethylenediaminetetraacetic acid, etc. and monocarboxylic acids such as lactic acid, gluconic acid, gallic acid, ascorbic acid, N-bis(2-hydroxyethyl)glycine (bicine) (2-(bis(2-hydroxyethyl)amino)acetic acid) and salts of any of these acids and mixtures of one or more of the said organic acids and their salts.

[0066] Component C), namely copper ions, preferably copper (II) ions, can be present in the bismuth conversion coating composition in an amount of about 1 to 300 ppm, 1.5 to 200 ppm, 2 to 150 ppm, 3 to 100 ppm, 3.5 to 75 ppm, 4 to 50 ppm, 4.5 to 25 ppm, or 5 to 20 ppm. Non-limiting examples of suitable materials for Component C) can include water-soluble and / or acid-soluble inorganic and organic copper sources, such as copper hexafluorosilicate, hydroxide, nitrate, chloride, phosphate, and sulfate, as well as acetate, citrate, formate, gluconate, tartrate, and other organic salts, and oxides, selenite, selenite, etc. Any inorganic or organic Cu(II) source can be used, provided that the Cu(II) source provides Cu(II) ions that dissolve in the conversion coating composition as disclosed herein, are at least partially deposited in the conversion coating on the metal substrate, and do not negatively affect the objectives and benefits of the present invention. Preferably, copper sulfate (II), copper nitrate (II), copper oxide (II), copper hydroxide (II). Combinations of two or more different copper compounds can be used.

[0067] Component D), namely one or more metal etchants, can contain a source of free fluoride ions, such as HF and / or a complex fluoroacid, which can be present as a source of fluoride ions, preferably a complex fluoroacid or its salt. The complex fluoroacid can be selected from fluoroacids of the general formula H2XF6, where X can be Ti, Zr, Hf, and Si; salts of these fluoroacids can also be used in the present invention. Generally, the amount of Component D), such as HF, complex fluoroacid, and / or its salt, that can be used in the bismuth conversion coating composition is about 0 to 5000 ppm, 100 to 4500 ppm, 200 to 4000 ppm, 300 to 3500 ppm, 400 to 3000 ppm, 450 to 2500 ppm, 500 to 2000 ppm, 525 to 1500 ppm. Component D) ideally can provide a reservoir of free fluoride ions. Generally, the amount of free fluoride ions that can be used in the bismuth conversion coating composition is about 0 to 5000 ppm, 1 to 4000 ppm, 3 to 3000 ppm, 4 to 2000 ppm, 5 to 1000 ppm, 6 to 500 ppm, 8 to 200 ppm, or 10 to 100 ppm. Free and complex fluoride ions serve to increase the etching of the metal substrate surface.

[0068] Component E), i.e., the pH regulator, can be in the form of an acid, a base, or a buffered acid / base combination. In the bismuth conversion coating composition, preferably, the pH is in the range of 2 to 6. When the pH is less than 2, etching becomes excessive; thus, it is impossible to form a sufficient coating. When the pH exceeds 6, etching becomes insufficient; thus, a good coating cannot be obtained, and precipitation of bath components may occur. 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. To control the pH of the chemical conversion coating agent, acidic compounds such as nitric acid and sulfuric acid, and basic compounds such as sodium hydroxide, potassium hydroxide, and ammonia can be used. Methods for adjusting the pH level to within the ranges of 2 - 6, 2.5 - 5, 2.75 - 4.5, and 3 - 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 base and / or at least one organic base. Suitable examples of pH regulators that can be used in the bismuth conversion coating composition as described herein include NaOH, KOH, ammonium hydroxide, ammonium bicarbonate, ammonium carbonate, sodium bicarbonate, sodium carbonate, potassium bicarbonate, potassium carbonate, and Bi(OH)3.

[0069] Component F), i.e., nitrate ions, desirably are present and can be provided as a counterion or a partial counterion to other components of the bismuth conversion coating composition, as non - limiting examples, such other components as component A), and if present, D) and F). Thus, suitable sources of component F) can include nitric acid, bismuth(III) nitrate pentahydrate; bismuth oxynitrate, and nitrates of copper nitrate and Group IVB metals, and preferably sodium nitrate and nitric acid if there are counter cations. Nitrate ions desirably are present in an amount of about 0 to 10,000 ppm, 15 to 9000 ppm, 30 to 8000 ppm, 45 to 7000 ppm, 60 to 6000 ppm, 75 to 5000 ppm, 90 to 4000 ppm, 100 to 3500 ppm, or 75 to 3000 ppm. Any inorganic or organic nitrate ion source that does not have a negative impact on the objectives and benefits of the present invention can be used. Combinations of two or more different nitrates can be used.

[0070] Additional components of the bismuth conversion coating composition can include:

[0071] Component G), i.e., Group IVB metals, can be present in the bismuth conversion coating composition and in the resulting coating. Desirably, the Group IVB metals can be selected from: Zr, Ti, and Hf and combinations thereof, preferably Zr and Ti. Generally, the amount of Component G) that can be used in the bismuth conversion coating composition is 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, 70 to 150 ppm. Non-limiting examples of suitable materials for Component G) can include water-soluble and / or acid-soluble, inorganic and organic sources of Group IVB metals, such as: fluotitanic acid H2TiF66; fluozirconic acid H2ZrF6; basic zirconium 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. The Group IVB metal fluoroacids can also optionally provide at least a portion of Component D), i.e., one or more metal etchants.

[0072] Component H), i.e., one or more accelerators, can be present in the bismuth conversion coating composition. Due to the relatively rapid deposition, conversion coating compositions generally do not require the presence of accelerators, as shown by the examples without accelerators. If desired, one or more coating accelerators in an amount of 1 to 5000 ppm can be included, preferably oxidation accelerators such as peroxides, iron(III) ions, nitrite ions, hydroxylamine, persulfate ions, sulfite ions, dithionite ions, and halogen-based ions such as sodium chlorate. Non-limiting examples of suitable materials for Component H) can include water-soluble and / or acid-soluble accelerators that can accelerate the deposition reaction of the bismuth conversion coating composition without having a harmful effect on the working bath or the deposited coating, such as hydroxylamine (which can be provided as a salt such as hydroxylamine sulfate); peroxides, preferably hydrogen peroxide; sodium nitrophenylsulfonate; sodium nitrite, nitroguanidine, oximes, etc. The amount of Component H) varies with the type of accelerator used, and selecting the appropriate amount is within the knowledge of one of ordinary skill in the art of conversion coatings. Generally, the amount of Component H) that can be used in the bismuth conversion coating composition can be 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, 70 to 150 ppm. Alternatively, for less active accelerators or those that, for example, have a rapidly decreasing concentration due to decomposition, in addition to the previously disclosed ranges, the upper limit of the accelerator dose can also include concentrations of 1000 ppm, 900 ppm, 800 ppm, 700 ppm, or 600 ppm.

[0073] Although a satisfactory bismuth coating is deposited by the bismuth conversion coating composition in the absence of a polymer, component I), i.e., one or more water-soluble and / or water-dispersible polymeric components, can advantageously be included in the bismuth conversion coating composition if desired. Generally, the amount of component I) that can be used in the bismuth conversion coating composition is 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, 70 to 150 ppm. Non-limiting examples of suitable materials for component I) include: (i.1) poly(hydroxystyrene) polyhydroxyalkylamino derivatives as described in more detail in U.S. Patent No. 4,963,596, the entire disclosure of which is hereby incorporated by reference herein to the extent not inconsistent with any explicit statement herein; (i.2) epoxy polymers, particularly polymers of diglycidyl ether of bisphenol-A, optionally terminated with non-polymerizable groups at the ends and / or having some epoxy groups hydrolyzed to hydroxyl groups; (i.3) polymers and copolymers of acrylic acid and methacrylic acid and their salts; (i.4) organic polymeric components selected from phenalkamine compounds, polyamide-type amine compounds, catechol compounds, and catechol copolymers; and (i.5) polymers and copolymers containing silicon, which can be organic and / or inorganic polymers.

[0074] As used herein, the term "phenalkamine compound" refers to a molecule containing a benzene ring and having at least three functional groups attached to the benzene ring: a) an OH group (i.e., a hydroxyl group); b) a C6-C30 saturated or unsaturated alkyl group; c) an amine-functionalized substituent such as an amino-alkyl substituent. According to one embodiment of the present invention, the phenalkamine compound can correspond to formula (I):

[0075] R-Ar(-OH)-CHR’NHCH2CH2(NHCH2CH2) n NH2(I)

[0076] wherein 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 (e.g., a C1-C6 or C1-C3 alkyl group such as methyl, ethyl, propyl, etc.), and n is an integer of 0 or at least 1, 2, 3, 4, 5 and not greater than 20, 18, 16, 14, 12, 10, 8 or 6, preferably 1-4.

[0077] According to one embodiment, a) and c) are adjacent to each other; that is, they are attached to adjacent carbon atoms of the benzene ring. According to a further embodiment, b) is attached to a carbon atom of the benzene ring which is separated from each carbon atom to which a) and c) are attached by at least one carbon atom of the benzene ring. In another embodiment, c) is in the ortho position to the hydroxyl group and b) is in the meta position to a). The benzene ring may bear one or more additional non-hydrogen substituents other than those stated in formula (I), such as alkyl groups (e.g., methyl, ethyl) and hydroxyl groups (other than a). For example, a second optional hydroxyl group may be present in the meta position to c) on the benzene ring. In one embodiment, the phenolic amine compound may be free of a hydroxyl group in the ortho position to a). The amine-functionalized substituent c) may comprise one or more amino groups, preferably primary and / or secondary amino groups, substituted on an alkylene group, wherein the alkylene group is attached 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 phenolic amine compounds may also be used. Desirably, the phenolic amine polymer has a weight average molecular weight of from 200 to 2000 daltons. The phenolic amine is further described in co-pending international application PCT / 2019 / 065127, which is incorporated herein by reference in its entirety.

[0078] As used herein, the term "polyamide-type amine compound" refers to a linear or branched, saturated or unsaturated organic polymer comprising a plurality of amide functional groups and optionally present amine and / or imidazoline functional groups. The polymer may comprise tertiary nitrogen atoms, a plurality of branches and / or at least some imidazoline functional groups having amide bonds in their substituents. Desirably, the polyamide-type polyamine polymer has a weight average molecular weight of from 200 to 10,000. The polyamide-type amine is further described in more detail in international patent publication WO2016167928, which is incorporated herein by reference in its entirety.

[0079] The term "catechol compound" refers to 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, for example dopamine and 3,4-dihydroxy-L-phenylalanine. A "catechol copolymer" refers to a reaction product of at least one catechol / catechol derivative with at least one co-reactive compound having one or more functional groups reactive therewith (where the co-reactive compound can for example be an amine, especially a polyamine such as polyethyleneimine, or a (meth)acryloyl-functionalized compound such as methacryloylaminoethyl ethylene urea) and their salts and mixtures. Desirably, the catechol copolymer has a weight-average molecular weight of from 200 to 10,000 daltons. Catechol, catechol derivatives and polymerization reaction products are described in more detail in International Patent Publication WO2018119368, which is incorporated herein by reference in its entirety.

[0080] Other additives known in the field of metal pretreatment can be included in the bismuth conversion coating compositions disclosed herein, provided that the additive does not interfere with the deposition and performance of the bismuth conversion coating. Additives can include surfactants, oxidants (other than accelerators), thickeners, rheology modifiers, dispersants, antimicrobial agents, biostabilizers, adhesion promoters, and the like.

[0081] Some materials, such as metallic elements, can be present in the conversion coating compositions as additives or as contaminants, such as metals of Groups IIB, VB-VIIB, VIII, IIIA&IVA, and Sb. These metallic elements can be used as additives provided that the additive does not interfere with the deposition and performance of the bismuth conversion coating. In some embodiments, such metals are not intentionally added to the bismuth conversion coating compositions disclosed herein and are preferably omitted, but may be present as unavoidable contaminants.

[0082] While brighteners such as plating brighteners, for example naphthalene-disulfonic acid, diphenylsulfonate, arylsulfonamide, azo dyes, etc. are not preferred, they can be included as an optionally present component in the bismuth conversion coating compositions disclosed herein, provided that the brightener does not interfere with the deposition and performance of the bismuth conversion coating. In a preferred embodiment of the bismuth conversion coating compositions disclosed herein, there is no brightener, as the brightener increases the cost of the product and is generally omitted.

[0083] Preparation method

[0084] The bismuth conversion coating composition of the present invention can be prepared using any suitable technique known in the art. In one embodiment, the bismuth conversion coating composition can be prepared by combining B), i.e., at least one water-soluble organic chelating agent, with water, preferably distilled water, and then adding A), i.e., the dissolved and / or dispersed bismuth source, with stirring to form a mixture. Thereafter, the pH of the mixture is adjusted to a selected bath operating pH value.

[0085] In a preferred embodiment, B) can comprise one or more water-soluble organic acids and preferably the pH range can be adjusted to about 2 - 6 by adding an alkaline substance such as a dilute ammonium bicarbonate solution. Other base sources such as sodium hydroxide can be used to increase the pH value provided that they do not interfere with the deposition and performance of the conversion coating.

[0086] After adjusting the pH to the operating conditions, the conversion coating composition desirably contains Bi(III) ions and can contain a colloidal dispersion of bismuth particles. Based on the operating pH, the bismuth conversion coating composition can contain the anions of the dissociated water-soluble organic chelating agent.

[0087] As used herein, when referring to a mixture (whether a solution or a dispersion), the term "storage stable" means that after an observation period of storing in a sealed container at 20 °C for at least 3 months and during which the mixture is not mechanically disturbed, the mixture does not exhibit phase separation and no precipitation or sedimentation of any substance visible to the human eye.

[0088] According to aspects of the present invention, at least one aqueous mixture of the bismuth conversion coating composition is brought into contact with the surface of a bare metal substrate. Such an aqueous mixture (which can be in the form of a solution or a dispersion and is preferably a storage stable mixture) can be formed by any suitable method. For example, the aqueous mixture can be used directly or after diluting the aqueous mixture to a specifically desired final use concentration. Water alone can be used for such dilution, but in other embodiments of the present invention, it is contemplated that one or more other types of components can be included in the aqueous mixture. For example, acids, bases, or buffers can be combined into the aqueous solution to alter its pH characteristics. In certain embodiments of the present invention, when in contact with the surface of a bare metal substrate (i.e., when used in a working conversion coating bath), the pH of the aqueous mixture can be, for example, 2 - 6, 2.5 - 5, 2.75 - 4.5, 3 - 4.

[0089] Over time, an aqueous mixture (working bath) that repeatedly contacts the surface of a bare metal substrate may become depleted in terms of the concentration of bismuth compounds and other components (such as copper). If this occurs, the aqueous mixture in the working bath can be replenished by adding individual components or a supplement containing a combination of components including the amount of bismuth compound etc. whose amount needs to be adjusted to provide effective restoration of the required concentration. The composition according to the present invention can be provided in two parts, where part A can contain, for example, bismuth, copper, and other components that do not precipitate with Bi and / or Cu, such as nitric acid and / or one or more chelating agents, while part B can contain one or more chelating agents, a fluorine-containing compound, and other components. In one embodiment, the supplement for the bismuth conversion coating bath contains bismuth, copper, and nitric acid, optionally in the form of an easily dispersible slurry. In addition, it should be understood that a repeatedly used working bath containing an aqueous mixture may accumulate a certain amount of various components brought in from the cleaning stage, such as alkaline detergents (sodium hydroxide, potassium hydroxide, alkali metal carbonates, alkali metal bicarbonates, phosphates, silicates), surfactants, and oil / fat / dust contaminants. When the content of such components reaches a level where the performance of the working bath or the quality of the converted-coated metal substrate being processed is adversely affected, the contents of the working bath can be discarded and replaced or the contents can be treated to remove or reduce such components or otherwise counteract their effects (e.g., by pH adjustment and / or ion exchange).

[0090] metal substrate

[0091] The present invention can be particularly used to treat the surface of a metal substrate vulnerable to corrosion, especially a bare metal surface to be painted. For example, a metal substrate containing iron (ferrous) can 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 metallic zinc, zinc alloys, such as electrogalvanized steel, galvalume, galvanneal, and hot-dipped galvanized steel; magnesium alloys; aluminum alloys, and aluminized steel substrates. A component or article containing more than one type of metal substrate can be processed according to the procedures described herein. The present invention can also be implemented using such a metal substrate, where a ferrous component or layer is covered with a non-ferrous metal coating (such as a zinc coating), and the ferrous component or layer is exposed due to cutting, forming, assembling, sanding, grinding, polishing, scratching, or other such operations.

[0092] cleaning step

[0093] As used herein, the term "bare metal substrate surface" refers to the metallic surface of a metal substrate, which metallic surface is substantially free of any contaminants and is not coated with a conversion coating or some other substance other than a natural oxide that may be present by reaction of the metal element with oxygen in the atmosphere. According to certain aspects of the present invention, a bare metal substrate surface to be pretreated with a bismuth conversion coating composition is obtained by cleaning a contaminated metal substrate surface using any cleaning procedure and materials known or conventionally used in the art (e.g., including mild or strong alkaline cleaners, neutral cleaners, and acidic cleaners) to remove grease, oil, dust, or other foreign substances and contaminants. Methods for cleaning metal surfaces are described, for example, in Murphy's "Metal Surface Treatments, Cleaning", Kirk - Othmer Encyclopedia of Chemical Technology, 2000. Aqueous and non - aqueous (i.e., organic solvent - based) cleaners can be employed. Components of suitable cleaners can include, for example, inorganic bases (e.g., alkali metal hydroxides, alkali metal carbonates, alkali metal bicarbonates), builders (e.g., phosphates, silicates), surfactants, water, organic solvents, etc. Examples of alkaline cleaners include cleaner ZX - 1, cleaner 315, and C - AK T51, each of which is available from Henkel Corporation, Madison Heights, Michigan. Any suitable method such as spraying, dipping, wiping, etc. can be used to apply the cleaner to the metal substrate surface and bring it into contact with the metal substrate surface. During contact, the cleaner temperature can be, for example, about 20 °C to 60 °C, but can be lower or higher temperatures that do not have a negative impact on the process. The contact duration between the cleaner and the metal substrate can be any time effective to achieve the desired degree of contaminant removal (e.g., 10 seconds to 5 minutes). Mechanical action can be utilized to assist in removing contaminants. Although the cleaners used for this purpose are typically in liquid or solution form, mechanical means such as sanding, sandblasting, or blasting with other dry media can also be used alone to clean the metal substrate surface. After the cleaning step, the metal substrate can optionally be subjected to one or more additional steps before being brought into contact with a solution or dispersion containing a reaction product of one or more pre - formed catechol compound / cocatalyst compounds. For example, the metal substrate surface can be rinsed one or more times with water and / or an acidic aqueous solution after cleaning.

[0094] A bare metal substrate surface can also be prepared by methods of forming or modifying a metal article that result in the production of a bare metal surface, such methods as cutting, scoring, filing, grinding, abrading, shot peening, sanding, etc.

[0095] Conversion coating step

[0096] After any cleaning step, the surface of the metal substrate is subjected to a conversion coating step by contact with the bismuth conversion coating composition of the present invention. The conversion coating step can be carried out immediately after the cleaning step, or after the optional deoxidation and / or additional rinsing steps as described above, or after a prolonged period of time after the cleaning step.

[0097] According to the present invention, an aqueous mixture comprising one or more bismuth compounds is brought into contact with the surface of the cleaned metal substrate. This contact can be accomplished by any suitable method, such as spraying, immersion, dipping, brushing, roll coating, etc. Generally, during this contact, the aqueous mixture is maintained at ambient temperature (e.g., room temperature) to a temperature moderately above ambient temperature. For example, the temperature of the aqueous mixture in the working bath can be 10 to 54 °C, 16 to 49 °C, 25 to 36 °C, or 32 to 43 °C.

[0098] The contact time should be selected to be sufficient to deposit an effective amount of the bismuth conversion coating on the surface of the bare metal substrate, which is generally considered to be an amount that effectively reduces the amount of corrosion on the metal surface compared to a control of the surface of the bare metal substrate measured under the same conditions, according to ASTM B117-19. Generally, a contact time 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 range covered by the disclosed ranges) can be appropriately selected.

[0099] Once the desired contact time with the bismuth conversion coating composition has been reached, the contact is stopped and the converted-coated metal substrate can be subjected to further processing steps. For example, spraying can be stopped or the article containing the converted-coated metal substrate can be removed from the immersion bath. The residual or excess aqueous mixture can be drained from the surface of the metal substrate. The removal of the residual or excess aqueous solution can be accomplished by any suitable method or combination of methods, such as draining, scraping with a squeegee, wiping, draining, or rinsing with water. According to certain embodiments, the surface of the converted-coated metal substrate can be dried (e.g., air-dried, heated, or oven-dried). In other embodiments, the converted-coated metal substrate is not dried before further processing steps such as sealing, painting, etc. (non-limiting examples include electrophoretic coating with paint).

[0100] It has been demonstrated that a conversion coating of bismuth and the metal oxide of the substrate metal can be deposited on the metal substrate, which provides corrosion resistance comparable to that of tricationic zinc phosphate for the final painted component.

[0101] In one embodiment, the bismuth conversion coating composition can be applied to the surface of a reactive metal substrate by contacting the metal substrate with the bismuth conversion coating composition at a temperature of 24 to 40 °C for about 2 minutes. The contacting can be achieved by any suitable means, including but not limited to dipping, spraying, roll coating, etc. The contact time and temperature can vary, but are typically less than 10 minutes, preferably less than 5 minutes. Desirable contact times are at least about 1, 3, 5, 10, 15, 20, 30, 40, 50 or 60 seconds and not more than about 9, 8, 7, 6, 5, 4, 3 or 2 minutes. Desirable temperature ranges are at least about 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31 or 32 °C and not more than about 40, 39, 38, 37, 36, 35, 34. Higher or lower temperatures can be used, such as at least above the freezing point of the bath and up to 50 °C, provided that the temperature does not interfere with the deposition of the conversion coating and has no negative impact on the performance of the metal bismuth conversion coating bath or the conversion coating.

[0102] Without being bound by a single theory, contacting the metal substrate with the aqueous acidic bismuth conversion coating composition results in several reactions: oxidation of the substrate (M 0 →M n+ +n e , M = Fe, Zn, Al), local pH increase due to the reduction of H + resulting in the deposition of Bi 3+ on the substrate metal surface as a mixture of bismuth oxides and / or hydroxides with substrate elements (Fe, Zn, Al).

[0103] Post-treatment

[0104] The present invention can also be part of a multi-step process, where the freshly deposited bismuth conversion coating is post-treated and / or seal rinsed prior to painting.

[0105] Non-limiting examples of suitable post-treatments include contacting the freshly deposited bismuth conversion coating with an acidic aqueous post-treatment composition that contains one or more Group IV metals of the Periodic Table such as Zr, Ti, and Hf, and typically also contains other components (such as metal etchants (e.g., fluorides), and optionally copper and / or nitrates and / or zinc and / or silicon-based materials). Such acidic aqueous post-treatment compositions are sometimes referred to as Group IV metal oxide deposition compositions (e.g., zirconia deposition compositions). The acidic aqueous post-treatment composition can, for example, have a pH of 5.0 or less and contain: at least one Group IV metal at 50 to 750 ppm; 0 to 50, 1 to 50, or 5 to 50 ppm of copper; 10 to 100 ppm of free fluoride ions; optional nitrates; and optional Si-based materials such as silanes, SiO2, silicates, etc. Optionally, the post-treatment can be a complex post-treatment that also includes 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 the surface by contacting the metal substrate with the acidic aqueous post-treatment composition for a sufficient length of time to form a Group IV metal oxide on at least a portion of the metal substrate surface. The contacting can be accomplished by any suitable means including, but not limited to, dipping, spraying, roll coating, etc. The contact time and temperature can vary, but are typically less than 10 minutes, preferably less than 5 minutes. Desirable contact times are at least about 1, 3, 5, 10, 15, 20, 30, 40, 50, or 60 seconds and not more than about 9, 8, 7, 6, 5, 4, 3, or 2 minutes. Desirable temperature ranges are at least about 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, or 32 °C and not more than about 40, 39, 38, 37, 36, 35, 34, or 33 °C. Higher or lower temperatures can be used, e.g., at least above the freezing point of the bath and up to 50 °C, provided that the temperature does not interfere with the deposition of the conversion coating and does not have a negative impact on the performance of the metal bismuth conversion coating working bath or the conversion coating.

[0106] A suitable seal rinse can desirably be an aqueous rinse, but can optionally contain organic solvents. The seal rinse can contain organic polymers, inorganic polymers, or combinations thereof. The seal rinse typically contains water-soluble and / or water-dispersible polymers that coalesce, crosslink, or otherwise form a seal layer on the conversion-coated metal substrate when dried without or without heating. The pH value of the seal rinse can typically be about 4 - 10.

[0107] For the purposes of this invention, the seal rinse is distinguished from "paint" by the following differences:

[0108] · The thickness of the organic sealant rinse layer is typically about 0.05 to 2.0 microns (wet film), while the thickness of the paint film is typically between 15 - 500 microns (wet film).

[0109] · The dry film thickness of the organic sealant layer is typically 0.01 to 1.0 microns, as measured by Glow Discharge Optical Emission Spectroscopy. The dry film thickness of the paint layer is at least about 15 microns, typically about 1 mil (25.4 microns), 1.5 mils (38.1 microns) or greater, and the total paint thickness of typical vehicle paints is about 3 - 5 mils (76.2 to 127 microns).

[0110] · The organic sealant rinse typically contains up to about 0.5 wt% organic solids, while the paint composition typically contains at least about 5 wt% to up to about 60 wt% organic solids.

[0111] Non - limiting examples of polymers suitable for the sealant rinse include, by way of non - limiting illustration, epoxy resins, phenolic resins, acrylic - type resins, polyurethanes, polyesters, and polyimides and combinations thereof. In one embodiment, an organic polymer selected from epoxy resins, phenolic resins, and polyimides is used. Preferred polymers for forming the additional layer include phenol - based polymers and copolymers such as those produced from linear phenolic resins having a molar ratio of formaldehyde to phenol less than 1, and novolac resins having a molar ratio of formaldehyde to phenol greater than 1. Such polyphenol polymers can be prepared as known in the art, for example, according to U.S. Patent No. 5,891,952. The linear phenolic resin is desirably used in combination with a cross - linker to facilitate curing. In one embodiment, a novolac resin having a molar ratio of formaldehyde to phenol of about 1.5 is used to form a polymer additional layer on the bismuth conversion coating. The phenolic resin useful for forming the polymer layer desirably has a molecular weight of about 1000 to about 5000 g / mol, preferably 2000 to 4000 g / mol.

[0112] In some embodiments, the water - soluble and / or water - dispersible polymer may contain functional groups that react with the elements in the bismuth conversion coating, and these functional groups can form bonds between the polymer and the coating. For example, uncured linear phenolic resins and novolac resins contain OH functional groups that can react with the metals in the bismuth conversion coating to link the polymer to the coating.

[0113] Optionally, Si-based materials such as silanes, SiO2, silicates, etc. can be used as sealants or can be used as additives. A sealant rinse can be applied to the surface of a metal substrate having a bismuth conversion coating deposited on at least a portion of the surface by contacting the metal substrate with the sealant rinse for a time sufficient to wet the bismuth conversion coating surface and / or form a sealant layer on at least a portion of the metal substrate surface. The contacting can be achieved by any suitable means that further enhances the corrosion resistance of the surface of the converted-coated metal substrate.

[0114] Application of additional coatings

[0115] After the conversion coating and any optional post-rinse (or "seal") steps, the metal substrate can be subjected to one or more further processing steps, particularly including the application of paint or other decorative and / or protective coatings. Any such coatings known in the art can be used, including for example electrophoretic coatings (E-coatings), solvent-based coatings, water-based coatings, powder coatings, etc. In such applications, the bismuth conversion coating or sealant can be used as a primer or corrosion protection layer.

[0116] Accordingly, the present invention can be practiced according to the following exemplary multi-step process:

[0117] 1) Cleaning of the metal substrate surface;

[0118] 2) Rinsing the cleaned (bare) metal substrate surface with an aqueous mixture comprising a reaction product of a pre-formed catechol compound / functionalized co-reactant;

[0119] 3) Conversion coating of the cleaned and rinsed metal substrate surface;

[0120] 4) Optionally rinsing the converted-coated metal substrate surface with water and / or a post-rinse solution or dispersion;

[0121] 5) Electrophoretic coating of the optionally rinsed converted-coated metal substrate surface;

[0122] 6) Rinsing the electrophoretically coated metal substrate surface with water; and

[0123] 7) Baking the rinsed electrophoretically coated metal substrate.

[0124] In this application document, the embodiments have been described in a manner that enables the application document to be written clearly and concisely, but it is intended and should be understood that the embodiments can be combined or separated in various ways without departing from the present invention. For example, it should be understood that all the preferred features described herein apply to all aspects of the present invention described herein.

[0125] In some embodiments, the inventions herein can be construed to exclude any element or method step that does not materially affect the basic and novel characteristics of the composition, article, or method. Additionally, in some embodiments, the present invention can be construed to exclude any element or method step not specified herein.

[0126] Although the present invention has been illustrated and described herein with reference to specific embodiments, the present invention is not intended to be limited to the details shown. Instead, various modifications may be made in the scope and range of equivalents of the claims and without departing from the present invention.

[0127] Examples

[0128] Example 1:

[0129] A conversion coating composition was prepared by combining the following by mixing:

[0130] Deionized water 99.72 wt%

[0131] Bismuth oxynitrate Bi5O(OH)9(NO3)4 0.08% (0.057 wt% Bi)

[0132] Lactic acid (88 wt%) 0.20 wt%.

[0133] The pH of the mixture = 2.7. The above mixture was added to deionized water as follows, which raised the pH value to 3.1: deionized water 75%, mixture 25%. A 10% ammonium bicarbonate solution ( M-AD 700) was used to increase the pH value until pH = 3.5 was achieved. This produced a clear straw-yellow solution containing 143 ppm Bi and 440 ppm lactic acid.

[0134] The solution was warmed to 32 °C. An ACT CRS plate was immersed in the bismuth conversion coating composition (the method is described below). This produced a distinct black coating that contained the elements Bi, O, and Fe.

[0135] Plate coating method: A bare metal plate available from ACT Laboratories, Inc. was used as the sample to be coated. Unless otherwise specified, the coating method is described below.

[0136] Bismuth conversion coating method

[0137] Cleaning: C-AK T51 (2% v / v, 49 °C, free alkalinity (hereinafter referred to as "FAlk") 5.0, spray for 90 seconds, 10 psi)

[0138] Rinse: City water (38 °C, spray for 60 seconds, 10 psi)

[0139] Rinse: Deionized water (21 °C, spray for 60 seconds, 10 psi)

[0140] Conversion coating: 32 °C, immersion for 120 seconds

[0141] Rinse: Deionized water (21 °C, spray for 60 seconds, 10 psi)

[0142] E-coating: BASF CathoGuard 800 (35 °C, soak for 240 seconds, constant current of 0.9 A ~ 230 V)

[0143] Rinse: Deionized water (24 °C, spray for 60 seconds, 10 psi)

[0144] Paint curing: Oven baking (185 °C, 35 minutes).

[0145] Comparative zinc phosphate coating method ( M-ZN 958)

[0146] Use a pretreated zinc phosphate-coated plate purchased from ACT Laboratories, Inc., where the total metal phosphate (hopeite and phosphophyllite) coating weight is 1.5 - 2.0 g / m². The zinc phosphate coating is applied according to the Henkel Technical Process Bulletin.

[0147] Rinse: Deionized water (21 °C, spray for 60 seconds, 10 psi)

[0148] E-coating: BASF CathoGuard 800 (35 °C, soak for 240 seconds, constant current of 0.9 A ~ 230 V)

[0149] Rinse: Deionized water (24 °C, spray for 60 seconds, 10 psi)

[0150] Paint curing: Oven baking (185 °C, 35 minutes).

[0151] Obtain the glow discharge emission spectral element depth distribution on the plate coated according to the present invention, which confirms the elements present in the coating.

[0152] Example 2:

[0153] Prepare the conversion coating composition by combining the following substances through mixing:

[0154] Deionized water 92.22 wt%

[0155] Bismuth oxynitrate Bi5O(OH)9(NO3)4 0.58% (0.41 wt% Bi)

[0156] Lactic acid (88 wt%) 7.2 wt%

[0157] The pH of the mixture = 1.97. The above mixture was added to deionized water as follows, which raised the pH to 2.7: 95% deionized water, 5% mixture. A 10% ammonium bicarbonate solution ( M-AD 700) was used to increase the pH until pH = 3.5 was achieved. This produced a clear straw-yellow solution containing 209 ppm Bi and 3368 ppm lactic acid.

[0158] The solution was warmed to 32 °C. The ACTCRS plate was dip-coated with the bismuth conversion coating composition according to the application method described previously. This produced a distinct black coating that contained the elements Bi, O, and Fe.

[0159] Example 3:

[0160] The conversion coating composition was prepared by combining the following by mixing:

[0161] Deionized water 59.95 wt%

[0162] Fluorosilicic acid (25 wt%) 40.00%

[0163] Bismuth oxide Bi2O3 0.05% (0.045 wt% Bi)

[0164] pH = 1.10

[0165] A 10% ammonium bicarbonate solution ( M-AD 700) was used to increase the pH until pH = 3.5 was achieved. This produced a clear colorless solution containing 450 ppm Bi and 10% fluorosilicic acid.

[0166] The solution was warmed to 32 °C. The ACTCRS plate was dip-coated with the bismuth conversion coating composition according to the application method described previously. This produced a distinct black coating that contained the elements Bi, O, and Fe.

[0167] Example 4:

[0168] Example 3 was repeated using 0.05% bismuth oxynitrate Bi5O(OH)9(NO3)4 in place of 0.05% bismuth oxide Bi2O3, producing a mixture with pH = 1. A 10% ammonium bicarbonate solution ( Increase the pH value until pH = 3.5 is achieved. This results in a clear, colorless solution containing 357 ppm Bi and 10% fluorosilicic acid.

[0169] Warm the solution to 32 °C. Dip coat the ACTCRS plate with the bismuth conversion coating composition according to the application method described previously. This produces a distinct black coating that contains the elements Bi, O, and Fe.

[0170] Example 5:

[0171] Repeat Example 3 using 0.05% bismuth nitrate Bi(NO3)3 instead of 0.05% bismuth oxide Bi2O3, producing a mixture with pH = 1.2. Use 10% ammonium bicarbonate solution ( M-AD700) to increase the pH value until pH = 3.5 is achieved. This results in a clear, colorless solution containing 253 ppm Bi and 10% fluorosilicic acid.

[0172] Warm the solution to 32 °C. Dip coat the ACTCRS plate with the bismuth conversion coating composition according to the application method described previously. This produces a distinct black coating that contains the elements Bi, O, and Fe.

[0173] Example 6:

[0174] Prepare the conversion coating composition by combining the following by mixing:

[0175] Deionized water 94.25 wt%

[0176] Bismuth oxide Bi2O3 0.5% (0.45 wt% Bi)

[0177] Tartaric acid 5.25 wt%

[0178] The pH of the mixture = 1.7. Add the above mixture to deionized water as follows, which raises the pH value to 2.7: Deionized water 95%, mixture 5%. Use 10% ammonium bicarbonate solution ( M-AD700) to increase the pH value until pH = 3.5 is achieved. This results in a clear, colorless solution containing 224 ppm Bi and 2625 ppm tartaric acid.

[0179] Warm the solution to 32 °C. Dip coat the ACTCRS plate with the bismuth conversion coating composition according to the application method described previously. This produces a distinct black coating that contains the elements Bi, O, and Fe.

[0180] Example 7:

[0181] Prepare a conversion coating composition by combining the following by mixing:

[0182] Deionized water 94.17 wt%

[0183] Bismuthyl nitrate Bi5O(OH)9(NO3)4 0.58% (0.41 wt% Bi)

[0184] Tartaric acid 5.25 wt%

[0185] The pH of the mixture = 1.7. Add the above mixture to deionized water as follows, which raises the pH value to 2.7: deionized water 95%, mixture 5%. Use a 10% ammonium bicarbonate solution ( M-AD 700) to raise the pH value until pH = 3.5 is achieved. This produces a clear, colorless solution containing 209 ppm Bi and 2625 ppm tartaric acid.

[0186] Warm the solution to 32 °C. Dip coat an ACTCRS plate with the bismuth conversion coating composition according to the application method described previously. This produces a distinct black coating that contains the elements Bi, O, and Fe.

[0187] Example 8:

[0188] Prepare a conversion coating composition by combining the following by mixing:

[0189] Deionized water 99.30 wt%

[0190] Bismuth nitrate Bi(NO3)3 0.10 wt%

[0191] Fluorosilicic acid (25 wt%) 0.40%

[0192] Tartaric acid 0.20 wt%

[0193] The pH of the mixture = 2.0. Use a 10% ammonium bicarbonate solution ( M-AD 700) to raise the pH value until pH = 3.5 is achieved. This produces a clear, colorless solution containing 506 ppm Bi, 1000 ppm fluorosilicic acid, and 2000 ppm tartaric acid.

[0194] Warm the solution to 32 °C. Dip coat an ACTCRS plate with the bismuth conversion coating composition according to the application method described previously. This produces a distinct black coating that contains the elements Bi, C, O, and Fe.

[0195] Example 9:

[0196] Prepare a conversion coating composition by combining the following by mixing:

[0197] Deionized water 99.30 wt%

[0198] Bismuth nitrate Bi(NO3)3 0.10 wt%

[0199] Fluorosilicic acid (25 wt%) 0.40%

[0200] Tartaric acid 0.20 wt%

[0201] Copper nitrate (1.841% Cu) 0.05%

[0202] The pH of the mixture = 2.0. A 10% ammonium bicarbonate solution ( M-AD 700) was used to increase the pH until pH = 3.5 was achieved. This produced a clear, light blue / green solution containing 506 ppm Bi, 10 ppm Cu, 1000 ppm fluorosilicic acid, and 2000 ppm tartaric acid.

[0203] The solution was warmed to 32 °C. The ACTCRS plate was dip-coated with the bismuth conversion coating composition according to the application method described previously. This produced a distinct black coating that contained the elements Bi, O, C, Cu, and Fe.

[0204] Example 10:

[0205] Example 9 was repeated using 0.20 wt% ascorbic acid in place of 0.20 wt% tartaric acid, producing a mixture with a pH = 2.0. A 10% ammonium bicarbonate solution (M-AD 700) was used to increase the pH until pH = 3.5 was achieved. This produced a clear, light blue / green solution containing 506 ppm Bi, 10 ppm Cu, 1000 ppm fluorosilicic acid, and 2000 ppm ascorbic acid.

[0206] The solution was warmed to 32 °C. The ACTCRS plate was dip-coated with the bismuth conversion coating composition according to the application method described previously. This produced a distinct black coating that contained the elements Bi, O, Cu, and Fe.

[0207] Example 11:

[0208] A conversion coating composition was prepared by combining the following by mixing:

[0209] Deionized water 99.40 wt%

[0210] Bismuth nitrate Bi(NO3)3 0.10 wt%

[0211] Fluorosilicic acid (25 wt%) 0.40%

[0212] 0.10 wt% citric acid

[0213] 0.05% copper nitrate (1.841% Cu)

[0214] pH of the mixture = 2.0. A 10% ammonium bicarbonate solution ( M-AD 700) was used to increase the pH until pH = 3.5 was achieved. This resulted in a clear, pale blue / green solution containing 506 ppm Bi, 10 ppm Cu, 1000 ppm fluorosilicic acid, and 1000 ppm citric acid.

[0215] The solution was warmed to 32 °C. The ACTCRS plates were dip-coated with the bismuth conversion coating composition using the application method described previously. This resulted in a distinct grey / black coating that contained the elements Bi, O, C, Cu, and Fe.

[0216] Example 12:

[0217] The following compositions were used to deposit a bismuth conversion coating on a bare ACT CRS substrate by the application method described above, where the coating bath temperature was 32 °C:

[0218] 1. 450 ppm Bi, from Bi2O3, 10% fluorosilicic acid; pH = 3.5;

[0219] 2. 360 ppm Bi, from bismuthyl nitrate, 10% fluorosilicic acid; pH = 3.5;

[0220] 3. 250 ppm Bi, from bismuth nitrate, 10% fluorosilicic acid; pH = 3.5;

[0221] 4. 216 ppm Bi, from bismuthyl nitrate, 0.3% lactic acid; pH = 3.5;

[0222] 5. 720 ppm Bi, from bismuthyl nitrate, 1000 ppm fluorosilicic acid, 2000 ppm tartaric acid, 10 ppm Cu; pH = 3.5.

[0223] All five of these bismuth conversion coating compositions deposited a dark black bismuth conversion coating.

[0224] The alkali resistance of these conversion coatings was evaluated by exposure to 0.1 M NaOH (pH = 12.2) for a dipping time of 4 hours at a temperature of 21 °C. For comparison, bare ACT CRS coated with a commercially available zinc phosphate conversion coating ( M-ZN 958) was also evaluated using the same test conditions.

[0225] 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 with no signs of red rust / iron oxidation. The loss of bismuth was approximately 10% of the original weight. The zinc phosphate samples were 100% covered with red rust and there was a significant loss of the zinc phosphate coating (>50% of the original weight loss). In all cases, coating loss was determined using Glow Discharge Optical Emission Spectroscopy Elemental Depth Profiles (GDOES).

[0226] Example 13:

[0227] In this example, different types of ACT metal panels (CRS, EG, HDG, and Al6111 panels) were tested. A bismuth conversion coating composition according to Example 9 was prepared and the pH was raised using a 10% ammonium bicarbonate solution ( M-AD700) until a pH of 3.5 was achieved. This produced a clear, light blue / green solution containing 506 ppm Bi, 10 ppm Cu, 1000 ppm fluosilicic acid, and 2000 ppm tartaric acid. The solution was warmed to 32 °C and the solution had 72 ppm of free fluoride ions and a pH of 3.5.

[0228] ACT CRS, EG, HDG, and Al6111 panels were dip-coated according to the application method described previously. This produced a distinct black coating on each of the different metal substrate samples. Each bismuth conversion coating contained the elements Bi, O, C, and Cu, as well as the metals from their respective base substrates.

[0229] Example 14:

[0230] A conversion coating composition was prepared by combining the following by mixing:

[0231] Deionized water 99.30 wt%

[0232] Fluosilicic acid (25 wt%) 0.40%

[0233] Tartaric acid 0.20 wt%

[0234] Bismuthyl nitrate Bi5O(OH)9(NO3)4 0.07%

[0235] Glycoluril resin 200 ppm

[0236] Copper nitrate (1.841% Cu) 0.05%

[0237] The pH of the mixture = 1.97. The pH value was increased using 10% ammonium bicarbonate solution ( M-AD 700) until a pH of 3.5 was achieved. This produced a clear, pale blue / green solution containing 506 ppm Bi, 10 ppm Cu, 200 ppm glycoluril resin, 1000 ppm fluorosilicic acid, and 2000 ppm tartaric acid.

[0238] The solution was warmed to 32 °C. The ACTCRS plates were dip-coated with the bismuth conversion coating composition according to the application method described previously. This produced a distinct black coating on the CRS substrate, the coating containing the elements Bi, O, C, Cu, and Fe.

[0239] Example 15:

[0240] The conversion coating composition was prepared by combining the following by mixing:

[0241] Deionized water 99.30 wt%

[0242] Fluorosilicic acid (25 wt%) 0.40%

[0243] Tartaric acid 0.20 wt%

[0244] Bismuthyl nitrate Bi5O(OH)9(NO3)4 0.07%

[0245] Copper nitrate (1.841% Cu) 0.05%

[0246] Sodium nitrophenylsulfonate (SNBS) 100 ppm

[0247] The pH of the mixture = 2.08. The pH value was increased using 10% ammonium bicarbonate solution ( M-AD 700) until a pH of 3.5 was achieved. This produced a clear, pale blue / green solution containing 506 ppm Bi, 100 ppm SNBS, 1000 ppm fluorosilicic acid, and 2000 ppm tartaric acid.

[0248] The solution was warmed to 32 °C. The ACTCRS plates were dip-coated with the bismuth conversion coating composition according to the application method described previously. This produced a distinct black coating, the coating containing the elements Bi, O, C, Cu, and Fe.

[0249] Example 16:

[0250] In this example, different types of ACT metal plates (CRS, EG, HDG, and Al6111 plates) were coated and tested. The conversion coating composition was prepared by combining the following by mixing:

[0251] Deionized water 99.28 wt%

[0252] Bismuth oxynitrate Bi5O(OH)9(NO3) 4 0.07%

[0253] Fluorosilicic acid (25 wt%) 0.40%

[0254] Tartaric acid 0.20 wt%

[0255] Copper nitrate (1.841% Cu) 0.05%

[0256] The pH of the mixture = 2.08. A 10% ammonium bicarbonate solution ( M-AD 700) was used to increase the pH value until pH = 3.5 was achieved. This produced a clear, light blue / green solution containing 506 ppm Bi, 10 ppm Cu, 1000 ppm fluorosilicic acid, and 2000 ppm tartaric acid. The mixture also contained some undissolved bismuth oxynitrate (white solid).

[0257] ACT CRS, EG, HDG, and Al6111 plates were dip-coated according to the application method described previously. This produced a distinct black coating on each of the different metal substrate samples. Each bismuth conversion coating contained the elements Bi, O, C, and Cu, as well as the metals from their respective base substrates. According to the parameters specified above for the bismuth conversion coating, E-coating step, after the application of the bismuth conversion coating, the plates were painted with the cathodic electrophoretic paint BASF Catho Guard 800, without drying or interruption during this process. Paint application time = 4.0 minutes. For comparison purposes, the same paint application parameters were used to coat ACT plates coated with a commercially available tricationic zinc phosphate ( M-ZN 958) and including E-coating with BASF CathoGuard 800.

[0258] The E-coating appearance of the bismuth conversion-coated plates was smooth and uniform, without mapping defects. The cured paint color of the bismuth conversion-coated plates was significantly darker than that of the zinc phosphate-coated control plates. The thickness of the dry E-coating was measured, where the bismuth conversion coating provided a thickness comparable to that of the zinc phosphate control plates.

[0259] Dry film thickness of E-coating, mil

[0260]

[0261] Paint adhesion

[0262] The paint adhesion was evaluated using GMW14829 / 14704. Procedure GMW14704 includes three separate tests: initial cross - hatch, cross - hatch after 24 - hour water immersion, and cross - hatch after 48 - hour water immersion. After each cross - hatch, tape pull - off as defined by General Motors test methods was performed, where a higher percentage indicates better performance. The panels were tested in triplicate; different panels were used for the 24 - hour immersion and 48 - hour immersion tests.

[0263] Percentage (%) of paint retained after tape pull - off

[0264]

[0265]

[0266] The paint adhesion on the bismuth coating is comparable to that of the zinc phosphate reference.

[0267] Corrosion performance

[0268] The cyclic corrosion performance was evaluated using GMW14872, Exposure C (26 cycles, mass loss = 3.892 g). The test cycle is defined by General Motors' test methods and includes a series of exposures to moisture, water spray, and salt spray. The painted panels were scratched and subjected to 26 cycles. The panels were tested in triplicate.

[0269] Corrosion results, scribe creep (mm), the smaller the number, the better the performance

[0270] Conversion coating Zinc phosphate Zinc phosphate Bismuth Bismuth <![CDATA Substrate > Maximum value Average value Maximum value Average value CRS 8.8 4.7 5.0 2.9 EG 4.9 3.4 5.6 2.0 HDG 6.0 2.9 5.5 2.5 Al6111 0 0 0 0

[0271] The corrosion resistance of the bismuth coating is comparable to that of the zinc phosphate reference.

[0272] The coating weight and thickness of the bismuth conversion coating on some unpainted panels were characterized. The average bismuth conversion coating weight measured in terms of bismuth was determined using Niton Xl3t (X - ray fluorescence), and the coating thickness was determined using glow - discharge emission spectroscopy elemental depth (depth profile):

[0273] Bismuth conversion coating measurement results

[0274] <![CDATA Substrate > <![CDATA[Average bismuth coating weight (g / m 2 )]]> Maximum bismuth coating thickness (nm) CRS 0.9 800 EG 0.8 500 HDG 0.8 500 Al6111 0.8 250

[0275] Example 16’: Improved cleaning:

[0276] As described above, Example 16 was repeated on a second set of ACT panels, but the process was changed as follows: It will be adopted The single "cleaning" step of the C-AK T51 spray for 90 seconds was replaced with two sequential "cleaning" steps: 1) Apply the C-AK T51 spray for 60 seconds (10 psi), then immediately 2) Immerse in C-AK T51 for 120 seconds. After bismuth conversion coating and rinsing, the bismuth conversion coatings on some uncoated panels were characterized. The average bismuth conversion coating weight measured in terms of bismuth was determined using Niton Xl3t (X-ray fluorescence), and the coating thickness was determined using glow discharge emission spectroscopy elemental depth (depth profile):

[0277] Bismuth Conversion Coating Measurements

[0278] <![CDATA Substrate > <![CDATA[Average bismuth coating weight (g / m 2 )]]> Maximum bismuth coating thickness (nm) CRS 0.3 120 EG 0.2 120 HDG 0.3 120 Al6111 0.3 200

[0279] The E-coat appearance of the bismuth conversion coated panels was smooth and uniform, without mapping defects. The color of the cured paint on the bismuth conversion coated panels was significantly darker than that of the zinc phosphate coated control panels. The dry E-coat thickness was measured, and the bismuth conversion coating provided a thickness comparable to that of the zinc phosphate control panels.

[0280] Dry Film Thickness of E-Coat, mils

[0281]

[0282] Corrosion performance

[0283] Using GMW 14872, Exposure C was modified to use (29 cycles, mass loss = 4.065 g) to evaluate the cyclic corrosion performance of the Example 16' panels.

[0284] Corrosion Results, Scratch Creep (mm), the lower the number the better the performance

[0285] Conversion coating Zinc phosphate Zinc phosphate Bismuth Bismuth <![CDATA Substrate > Maximum value Average value Maximum value Average value CRS 7.5 3.6 5.0 3.4 EG 5.1 3.4 5.9 2.6 HDG 6.5 3.7 6.5 3.8 Al6111 0.6 0.1 0.6 0.1

[0286] Using a different test, the cyclic corrosion performance of the Example 16' panels was evaluated using Ford, L-467. The test cycle was defined by the test method of Ford Motor Company and included a series of exposures to moisture, water spray, and salt spray. The painted panels were scratched and tested for 6 weeks. The panels were tested in triplicate.

[0287] Corrosion Results, Scratch Creep (mm), the lower the number the better the performance

[0288] Conversion coating Zinc phosphate Zinc phosphate Bismuth Bismuth <![CDATA Substrate > Maximum value Average value Maximum value Average value CRS 3.8 2.7 4.0 2.8 EG 6.0 3.9 5.7 3.3 HDG 7.4 4.5 8.0 4.5

[0289] Example 17:

[0290] Repeat Example 16 using a reduced amount of tartaric acid (reduced from 0.20 wt% to 0.108 wt%). The mixture pH = 2.0. Use 10% ammonium bicarbonate solution ( M-AD 700) to increase the pH value until a pH = 3.5 is achieved. This produced a clear, light blue / green solution containing 506 ppm Bi, 10 ppm Cu, 1000 ppm fluorosilicic acid, and 1080 ppm tartaric acid. The solution was clear and had no undissolved (visible) solids.

[0291] Following the procedure of Example 16 resulted in a distinct black coating on each of the ACT CRS, EG, HDG, and Al6111 plates for each different metal substrate sample. Each bismuth conversion coating contained the elements Bi, O, C, and Cu, as well as the metals from their respective base substrates. The E-coat appearance was smooth and uniform with no mapping defects. The cured paint color of the bismuth conversion coated plates was significantly darker than that of the zinc phosphate coated control plates. The E-coat dry film thickness was comparable between the bismuth coating and the zinc phosphate coating control. Paint adhesion and corrosion resistance tests were conducted without immersion and with 48-hour immersion according to the procedure of Example 16, and the results are shown in the table below.

[0292] Percentage of paint retained after tape pull (%)

[0293] Substrate / conversion coating Initial - without soaking After soaking for 48 hours CRS Bismuth conversion coating 100 100 Zinc phosphate coating 100 98-100 EG Bismuth conversion coating 100 0 Zinc phosphate coating 100 100 HDG Bismuth conversion coating 100 0 Zinc phosphate coating 100 100 Al6111 Bismuth conversion coating 100 99-100 Zinc phosphate coating 100 99-100

[0294] Except for the EG and HDG substrates, the paint adhesion on the bismuth coating was comparable to the zinc phosphate control.

[0295] Corrosion results, scratch creep (mm), the lower the number the better the performance

[0296] Conversion coating Zinc phosphate Zinc phosphate Bismuth Bismuth <![CDATA Substrate > Maximum value Average value Maximum value Average value CRS 10.2 5.2 5.5 3.0 EG 5.2 1.7 5.4 2.9 HDG 4.2 2.0 4.6 2.6 Al6111 0 0 0 0

[0297] The corrosion resistance of the bismuth coating was comparable to the zinc phosphate control.

[0298] Example 18:

[0299] Repeat Example 16 using an increased amount of tartaric acid (increased from 0.20 wt% to 0.54 wt%). The mixture pH = 2.0. Use 10% ammonium bicarbonate solution ( M-AD 700) to increase the pH value until a pH = 3.5 is achieved. This produced a clear, light blue / green solution containing 506 ppm Bi, 10 ppm Cu, 1000 ppm fluorosilicic acid, and 5400 ppm tartaric acid. The solution was clear and had no undissolved (visible) solids.

[0300] Following the procedure of Example 16 resulted in visible black coatings on ACT CRS, EG, HDG, and Al6111 plates on each of the different metal substrate samples. Each bismuth conversion coating contained the elements Bi, O, C, and Cu, as well as the metals from their respective base substrates. The bismuth conversion coating on the CRS substrate was examined using a field emission scanning electron microscope (FESEM) at a maximum magnification of 100,000x. The bismuth conversion coating deposited on the CRS exhibited a complete substrate coverage with a uniform nodular structure. No exposed CRS substrate was observed. The E-coat appearance was smooth, uniform, and free of mapping defects. The cured paint color of the bismuth conversion-coated plates was significantly darker than that of the zinc phosphate-coated control plates. The E-coat dry film thickness was comparable between the bismuth coating and the zinc phosphate coating control. Paint adhesion and corrosion resistance tests were conducted without immersion and with 48-hour immersion according to the procedure of Example 16, and the results are shown in the table below.

[0301] Percentage of paint remaining after tape pull (%)

[0302] Substrate / conversion coating Initial - without soaking After soaking for 48 hours CRS Bismuth conversion coating 100 100 Zinc phosphate coating 100 98-100 EG Bismuth conversion coating 100 50 Zinc phosphate coating 100 100 HDG Bismuth conversion coating 100 95 Zinc phosphate coating 100 100 Al6111 Bismuth conversion coating 100 100 Zinc phosphate coating 100 100

[0303] The paint adhesion on the bismuth coating was comparable to that of the zinc phosphate control, except for the EG substrate.

[0304] Corrosion results, scratch creep (mm), the lower the number, the better the performance

[0305] Conversion coating Zinc phosphate Zinc phosphate Bismuth Bismuth <![CDATA Substrate > Maximum value Average value Maximum value Average value CRS 10.2 5.2 4.3 3.0 EG 5.2 1.7 5.0 2.8 HDG 4.2 2.0 4.26 2.6 Al6111 0 0 0 0

[0306] The corrosion resistance of the bismuth coating was comparable to that of the zinc phosphate control.

[0307] Example 19:

[0308] 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 value was increased using a 10% ammonium bicarbonate solution ( M-AD 700) until pH = 3.5 was achieved. This produced a clear light blue / green solution containing 506 ppm Bi, 10 ppm Cu, 1000 ppm fluorosilicic acid, and 1000 ppm sodium gluconate. The solution was clear and free of undissolved (visible) solids.

[0309] Following the procedure of Example 16 resulted in visible black coatings on ACT CRS, EG, HDG, and Al6111 plates on each of the different metal substrate samples. Each bismuth conversion coating contained the elements Bi, O, C, and Cu, as well as the metals from their respective base substrates.

[0310] Example 20:

[0311] Prepare a conversion coating composition by combining the following materials through mixing:

[0312] Deionized water 99.30 wt%

[0313] Fluorosilicic acid (25 wt%) 0.40%

[0314] Tartaric acid 0.20 wt%

[0315] Bismuthyl nitrate Bi5O(OH)9(NO3)4 0.07%

[0316] Polyamide-type amine resin 0.005%

[0317] The polyamide-type amine polymer additive is Versamid 150, commercially available from Gabriel Performance Products. It is a reaction product of dimer fatty acid and polyamine, described as having an MW of 200 to 10,000 daltons; amine content: 100 to 1000 mg KOH per gram of resin.

[0318] The pH of the mixture = 2.0. Use a 10% ammonium bicarbonate solution ( M-AD 700) to increase the pH value until pH = 3.5 is achieved. This results in a light yellow solution containing 506 ppm Bi, 50 ppm polyamide-type amine resin, 1000 ppm fluorosilicic acid, and 2000 ppm tartaric acid. The solution is clear and has no undissolved (visible) solids.

[0319] Warm the solution to 32 °C. Dip-coat the ACT CRS, EG, HDG, and Al6111 plates according to the application method described previously. This results in an obvious black coating on each different metal substrate sample. Each bismuth conversion coating contains the elements Bi, O, and C, as well as the metals from their respective base substrates.

[0320] Example 21:

[0321] Repeat Example 20 using 0.005% phenolic amine resin, which is a resin based on cashew nut shell liquid (cardanol, anacardic acid, cardolic acid) and polyamine, MW: = 200 to 2,000 daltons; amine content: 100 to 500 mg KOH / gram of resin, commercially available from Cardolite Corporation under the trade name Cardolite NX-8101, to replace 0.005% polyamide-type amine resin, to obtain a mixture with pH = 2.0. Use a 10% ammonium bicarbonate solution ( Increase the pH value until pH = 3.5 is achieved. This results in a pale yellow solution containing 506 ppm Bi, 50 ppm phenolic amine resin, 1000 ppm fluorosilicic acid, and 2000 ppm tartaric acid. The solution is clear and free of undissolved (visible) solids.

[0322] Warm the solution to 32 °C. Dip coat the ACT CRS, EG, HDG, and Al6111 plates according to the application method described previously. This results in a distinct black coating on each of the different metal substrate samples. Each bismuth conversion coating contains the elements Bi, O, and C, as well as the metal from their respective base substrates.

[0323] Example 22:

[0324] Repeat Example 16, where Ludox TMA (an aqueous dispersion (20%) of colloidal silica, commercially available from Grace Materials Technologies) is added in an amount of 0.025% to obtain a mixture with pH = 2.0. Use 10% ammonium bicarbonate solution ( M-AD 700) Increase the pH value until pH = 3.5 is achieved. This results in a clear light blue / green solution containing 506 ppm Bi, 10 ppm Cu, 50 ppm SiO2, 1000 ppm fluorosilicic acid, and 2000 ppm tartaric acid. The solution is clear and free of undissolved (visible) solids.

[0325] Warm the solution to 32 °C. Dip coat the ACT CRS, EG, HDG, and Al6111 plates according to the application method described previously. This results in a distinct black coating on each of the different metal substrate samples. Each bismuth conversion coating contains the elements Bi, O, C, Si, and Cu, as well as the metal from their respective base substrates.

[0326] Post-treatment after bismuth conversion coating

[0327] Example 23:

[0328] Zirconium-containing post-treatment agent

[0329] In this example, a zirconium-containing post-treatment agent is applied to the ACT CRS, EG, HDG, and Al6111 plates with bismuth conversion coatings to evaluate compatibility with the bismuth conversion coatings.

[0330] Dip coat the ACT CRS, EG, HDG, and Al6111 plates with the bismuth conversion coating composition of Example 16 according to the application method described previously, and then spray deposit the zirconium-containing post-treatment agent according to the following method:

[0331] Bismuth conversion coating / post-treatment method

[0332] Cleaning: C-AK T51 (2% v / v, 49 °C, FAlk 5.0, spray for 90 seconds, 10 psi)

[0333] Rinsing: Municipal water (38 °C, spray for 60 seconds, 10 psi)

[0334] Rinsing: Deionized water (21 °C, spray for 60 seconds, 10 psi)

[0335] Conversion coating: 32 °C, immersion for 120 seconds

[0336] Rinsing: Deionized water (21 °C, spray for 60 seconds, 10 psi)

[0337] Post-treatment: M-PT 54NC, acidic, chromium-free, zirconium-containing

[0338] Passivation post-treatment (0.5% v / v, 21 °C, pH = 4.0, spray for 60 seconds)

[0339] Rinsing: Deionized water (24 °C, spray for 60 seconds, 10 psi)

[0340] Air drying (ambient temperature, compressed air, 90 psi)

[0341] A distinct black coating was deposited on each ACT CRS, EG, HDG, and Al6111 metal substrate sample. Each bismuth conversion coating contained the elements Bi, O, C, and Cu, as well as the metals from their respective base substrates. The bismuth conversion coating was not significantly removed by reaction with the zirconium-containing post-treatment composition, indicating that an acidic post-treatment of the bismuth conversion coating could be carried out subsequently.

[0342] Example 24: Organic polymer sealant

[0343] The coating method of Example 23 was repeated using an organic polymer sealant instead of the zirconium-containing post-treatment agent. The organic polymer sealant was applied to ACT CRS, EG, HDG, and Al6111 plates with bismuth conversion coatings to evaluate its compatibility with the bismuth conversion coatings.

[0344] The ACT CRS, EG, HDG, and Al6111 plates were dip-coated with a bismuth conversion coating composition according to the application method of Example 23, and then 0.75% v / v was spray-deposited using the following parameters M-PT 99X (an organic polymer sealant): 21 °C, pH = 4.0, spray for 60 seconds.

[0345] A distinct black coating was deposited on each ACT CRS, EG, HDG, and Al6111 metallic substrate sample. Each bismuth conversion coating contains the elements Bi, O, C, and Cu, as well as the metals from their respective base substrates. By contacting / reacting with an organic polymer sealant composition, the bismuth conversion coating was not significantly removed, indicating that, if desired, the bismuth conversion coating can be suitable for organic polymer sealing.

[0346] Example 24’: Organic polymer sealant

[0347] The procedure of Example 24 described above was repeated on a second set of ACT plates, but the method was changed as follows: The single “cleaning” step of spraying with C-AK T51 for 90 seconds was replaced with two sequential “cleaning” steps: 1) spraying with C-AKT51 for 60 seconds (10 psi), followed immediately by 2) immersion in C-AK T51 for 120 seconds and replacing “air drying” with “E-coating: BASF CathoGuard 800 (35 °C, soak for 270 seconds, 0.9 amperes constant current ~230 V), rinse: deionized water (24 °C, spray for 60 seconds, 10 psi), and paint curing: oven bake (185 °C, 35 minutes).

[0348] The ACT CRS, EG, HDG, and Al6111 plates were dip-coated as described above. This resulted in a distinct black coating on each of the different metallic substrate samples. Each bismuth conversion coating contains the elements Bi, O, C, and Cu, as well as the metals from their respective base substrates. For corrosion performance evaluation, the plates were painted with the cathodic electrocoat BASF CathoGuard 800 according to the parameters stated above for the bismuth conversion coating and E-coating steps, without drying or interruption during this process. Paint application time = 4.5 minutes.

[0349] The E-coat appearance of the bismuth conversion-coated plates was smooth and uniform, without mapping defects. The cured paint color of the bismuth conversion-coated plates was significantly darker than that of the zinc phosphate-coated control plates. The thickness of the dry E-coat was measured, where the bismuth conversion coating provided a thickness comparable to that of the zinc phosphate control plates.

[0350] Dry film thickness of E-coating, mil

[0351]

[0352] Corrosion performance

[0353] Using GMW14872, Exposure C was modified to use: (29 cycles, mass loss = 4.065 g) The cyclic corrosion performance of the panel of Example 24’ was evaluated.

[0354] Corrosion results, scratch creep (mm), the smaller the value, the better the performance.

[0355] Conversion coating Zinc phosphate Zinc phosphate Bismuth Bismuth <![CDATA Substrate > Maximum value Average value Maximum value Average value CRS 7.5 3.6 4.7 2.7 EG 5.1 3.4 4.7 2.5 HDG 6.5 3.7 6.0 3.2 Al6111 0.6 0.1 0.0 0.0

[0356] Using different tests, the cyclic corrosion performance of the panel of Example 24’ was evaluated using Ford's L-467. The test cycle was defined by the test method of Ford Motor Company and included a series of exposures to moisture, water spray, and salt spray. The painted panel was scratched and tested for 6 weeks. The panels were tested in triplicate.

[0357] Conversion coating Zinc phosphate Zinc phosphate Bismuth Bismuth <![CDATA Substrate > Maximum value Average value Maximum value Average value CRS 3.8 2.7 3.5 2.3 EG 6.0 3.9 7.2 4.0 HDG 7.4 4.5 7.0 4.1

[0358] The above invention has been described in accordance with relevant legal standards, and thus the description is exemplary rather than restrictive in nature. Variations and modifications of the disclosed embodiments will be apparent to those skilled in the art and fall within the scope of the present invention. Therefore, the legal protection scope of the present invention can only be determined by studying the following claims.

Claims

1. An acidic aqueous bismuth conversion coating composition, comprising: A) dissolved and / or dispersed bismuth; B) at least one water-soluble organic chelating agent present in an amount sufficient to dissolve or disperse A); C) 1 to 25 ppm of dissolved copper ions; D) at least one metal etchant comprising a complex fluoroacid or a salt thereof, wherein the complex fluoroacid is selected from fluoroacids of the general formula H2XF6, where X is Ti, Zr, Hf or Si; and the acidic aqueous bismuth conversion coating composition has a pH in the range of 2.0 to 6.

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

3. The acidic aqueous bismuth conversion coating composition according to claim 2, wherein the one or more water-soluble organic acids and their salts are selected from aliphatic or aromatic; linear, branched or cyclic; saturated or unsaturated C3-C12 organic acids and their salts.

4. The acidic aqueous bismuth conversion coating composition according to claim 2, wherein the one or more water-soluble organic acids and their salts include at least one organic polycarboxylic acid and its salt.

5. The acidic aqueous bismuth conversion coating composition according to claim 4, wherein the at least one organic polycarboxylic acid and its salt includes substituted and / or unsubstituted α,ω-dicarboxylic acids.

6. The acidic aqueous bismuth conversion coating composition according to claim 5, wherein the substituted and / or unsubstituted α,ω-dicarboxylic acids and their salts include one or more of substituted and / or unsubstituted malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid and their salts.

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

8. The acidic aqueous bismuth conversion coating composition according to claim 1, which comprises less than 1 wt% of phosphoric acid and / or its salt and less than 1 wt% of nickel.

9. The acidic aqueous bismuth conversion coating composition according to claim 1, which comprises one or more additional components selected from sources of free fluoride ions, nitrate ions and Si-based substances.

10. The acidic aqueous bismuth conversion coating composition according to claim 1, wherein the acidic aqueous bismuth conversion coating composition comprises at least one pH regulator and has a pH of 2.5 to 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 5 to 10,000 ppm.

12. The acidic aqueous bismuth conversion coating composition according to claim 1, wherein the dissolved and / or dispersed bismuth includes one or more of bismuth nitrate, oxide and hydroxide.

13. The acidic aqueous bismuth conversion coating composition according to claim 1, wherein the dissolved and / or dispersed bismuth is selected from bismuth nitrate; bismuth nitrate pentahydrate; bismuthyl nitrate; 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 at a total concentration of 50 to 100,000 ppm.

15. A replenisher composition for replenishing the acidic aqueous bismuth conversion coating composition of claim 1 after use, comprising a storage-stable composition containing bismuth, copper, nitric acid and optionally nitrate ions.

16. A method of depositing a bismuth conversion coating on a substrate having a metal surface, comprising the steps of: a. contacting the metal surface of the substrate with the acidic aqueous bismuth conversion coating composition according to claim 1 for a time sufficient to form a bismuth conversion coating on at least a portion of the metal surface; and b. rinsing the bismuth conversion coating with a rinsing agent comprising water.

17. The method of depositing a bismuth conversion coating according to claim 16, wherein the metal surface of the substrate is selected from iron-containing metals, zinc-containing metals and aluminum-containing metals.

18. The method of depositing a bismuth conversion coating according to claim 16 or 17, further comprising step c): post-treating and / or sealing and rinsing at least a portion of the metal surface having the bismuth conversion coating before painting.

19. The method according to claim 16 or 17, wherein the method further comprises the step of coating at least a portion of the metal surface having the bismuth conversion coating with a cathodic electrodepositable electrophoretic dip coating, and wherein the metal surface is not dried after the rinsing step b) and before coating with the cathodic electrodepositable electrophoretic dip coating.

20. A substrate having a metal surface with a bismuth conversion coating deposited thereon, wherein the bismuth conversion coating is formed from the acidic aqueous bismuth conversion coating composition according to claim 1, wherein the bismuth conversion coating comprises bismuth oxide and / or bismuth hydroxide and further comprises at least one of the elements Cu, Cu(I) and Cu(II).

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