Two-step metal conversion coating applications utilizing bismuth compositions and zirconium compositions

Abstract

Provided are conversion coating systems and methods, and compositions used therein, as well as conversion-coated multi-metal articles wherein the systems and methods enable conversion coating of differentially constituted surfaces of multi-metal articles (such as those that include surfaces that are steel or galvanized steel, as well as aluminum-containing surfaces) producing uniform, contiguous conversion coatings, without the use of added heavy metals, preferably without phosphorus, and under reduced operating temperatures, which show excellent corrosion resistance and paint adhesion on such surfaces, as compared with conventional commercial pre-treatment comprising tri-cationic zinc phosphate.

Description

Two-Step Metal Conversion Coating Applications Utilizing Bismuth Compositions and Zirconium Compositions CROSS-REFERNCE

[0001] This PCT application claims priority to U.S. Provisional Patent Application No. 63 / 663855, filed June 25, 2024, the disclosure of which is hereby incorporated by reference in its entirety. TECHNICAL FIELD

[0002] The present disclosure pertains to conversion coatings for the pretreatment of metal surfaces. BACKGROUND

[0003] Tri-cationic zinc phosphate conversion coating systems are considered the performance benchmark for conversion coating technology. These zinc phosphate conversion coatings are traditionally considered necessary to provide the corrosion resistance and paint adhesion of the subsequent paint layering system.

[0004] However, the tri-cationic zinc phosphate has several negative attributes that end users would like to avoid or minimize: heavy metals, such as Co, Ni and Zn, which are undesirable in high concentrations due to their contribution to sludge formation with associated handling costs of filtration and waste disposal. Use of phosphorus containing material, e.g., phosphoric acid and phosphate ions that contribute to pollution, such as eutrophication of natural waterways, is also undesirable, as are relatively high operating temperatures with associated energy costs, and maintenance costs of a heat exchanger system. The automotive original equipment manufacturer (OEM) market has long desired a replacement product for tri-cationic zinc phosphate conversion coating systems. SUMMARY

[0005] Provided herein are conversion coating systems for sequential pretreatment of an article having a first portion comprising steel, galvanized steel, or alloy-galvanized steel, and a second portion comprising aluminum or an aluminum alloy, wherein the system comprises a first stage comprising (i) a first conversion coating working bath composition comprisingbismuth, for example, in a concentration of about 25 to 5000 ppm, and organic acid, for example, in a concentration of about 50-75,000 ppm, wherein the first conversion coating composition has an acidic pH, preferably in a range of about 2.0 to about 6.0, more preferably about 2.5 to 5.5 and a temperature of at least about 10°C during operation of the system and not more than 100°C, desirably about 10-70°C, preferably about 10-54°C; and, a second stage comprising (ii) a second conversion coating working bath composition comprising zirconium, for example, in a concentration of about 50-500 ppm; free fluoride, for example, in a concentration of about 10- 100 ppm; a total fluoride concentration of, for example, about 150-2,000 ppm; and, nitrate, for example, in a concentration of about 600-10,000 ppm; wherein the second conversion coating composition has an acidic pH, desirably about 3.0 to 6.0, preferably about 3.5-5.0 and a temperature of at least about 10°C during operation of the system and not more than 100°C, desirably about 20-65°C, preferably about 20-54°C, wherein contacting the article with the first conversion coating composition is effective to form a bismuth-containing conversion coating layer on the first portion of the article, and contacting the article with the second conversion coating composition, in sequence after the first conversion coating, is effective to form a different conversion coating layer on the second portion of the article. The first stage may include one or more cleaning, deoxidizing and / or pre-rinsing stations, preceding the first conversion coating working bath and a first rinsing station may follow the first conversion coating bath, and preferably may provide counter flow rinsing. The second stage includes the second conversion coating working bath desirably followed by at least one second rinsing station. To the extent counter flow rinsing is provided at the second rinsing station, it preferably does not flow to the first stage. The cleaning, deoxidizing, rinsing and conversion coating stages may include immersion tanks, sprayers, foggers or a combination thereof and may be optionally equipped with a reclaim receptacle and / or exit spray risers with spray nozzles to return any drag out. Physical features may also include carriers to move parts through the system.

[0006] The present disclosure also provides methods for conversion coating of a multi- metal article comprising (i) contacting a multi-metal article that comprises a first portion comprising steel, galvanized steel, alloy-galvanized steel, or any combination thereof, and a second portion comprising aluminum or aluminum alloy, with a first conversion coating composition comprising bismuth, for example, in a concentration of about 25 to 5000 ppm, and organic acid,for example, in a concentration of about 50-75,000 ppm, wherein the first conversion coating composition has an acidic pH, preferably in a range of about 2.0 to about 6.0, more preferably about 2.5 to 5.5 and a temperature of at least about 10°C during operation of the system and not more than 100°C, desirably about 10-70°C, preferably about 10-54°C, for a time sufficient to form on at least one surface of the first portion of the article a bismuth-containing conversion coating layer having a coating weight of about 50-5000 mg / m2, measured as elemental Bi; (ii) optionally, rinsing the multi-metal article with an aqueous rinse; and, (iii) contacting the multi-metal article with a second conversion coating composition comprising zirconium, for example, in a concentration of about 50-500 ppm; free fluoride, for example, in a concentration of about 10-100 ppm; a total fluoride concentration of, for example, about 150-2,000 ppm; and, nitrate, for example, in a concentration of about 600-10,000 ppm; wherein the second conversion coating composition has an acidic pH, desirably about 3.0 to 6.0, preferably about 3.5-5.0 and a temperature of at least about 10°C during operation of the system and not more than 100°C, desirably about 20-65°C, preferably about 20-54°C, for a time sufficient to form on at least one surface of the second portion of the multi-metal article a zirconium-containing conversion coating layer having a coating weight of about 10 to 200 mg / m2.

[0007] Also provided herein are multi-metal articles comprising (i) a zinciferous or ferrous surface with an adherent first conversion coating layer comprising bismuth deposited on the zinciferous or ferrous surface, and (ii) an aluminum or aluminum alloy surface with a second conversion coating layer comprising ZrO2on the aluminum or aluminum alloy surface, wherein the first conversion coating layer and the second conversion coating layer were produced by a presently disclosed method for conversion coating.

[0008] The present disclosure also provides multi-metal articles comprising a first portion comprising a zinciferous or ferrous surface and a first conversion coating layer on the zinciferous or ferrous surface, the first conversion coating comprising bismuth, a bismuth compound, or both present in an amount of about 50 to 5000 mg / m2Bi, measured as mass of the element bismuth present as determined via X-ray fluorescence; and, a second portion comprising an aluminum or aluminum alloy surface and a second conversion coating on the aluminum or aluminum alloy surface, the second conversion coating comprising ZrO2.Thesecond conversion coating is present in an amount of about 10-200 mg / m2Zr, which is measured as mass of the element zirconium as determined via X-ray fluorescence.

[0009] Below described are various aspects of the invention. Aspect 1 comprises a conversion coating system for sequential pretreatment of an article having a first portion comprising steel, galvanized steel, or alloy-galvanized steel, and a second portion comprising aluminum or an aluminum alloy, the system comprising: (i) a first conversion coating composition comprising dissolved and / or dispersed bismuth, and organic acid, wherein the first conversion coating composition has an acidic pH, desirably about 2.0 to 6.0, preferably about 2.5 to 5.5 and a temperature of at least about 10°C during operation of the system and not more than 100°C; and, (ii) a second conversion coating composition comprising zirconium; fluoride; and, nitrate; wherein the second conversion coating composition has an acidic pH, desirably about 3.0 to 6.0, preferably about 3.5-5.0 and a temperature of at least about 10°C during operation of the system and not more than 100°C, desirably about 20-65°C, preferably about 20-54°C, during operation of the system and not more than 100°C; wherein contacting the article and the first conversion coating composition is effective to form a bismuth-containing conversion coating layer on the first portion of the article, and contacting the article and the second conversion coating composition, in sequence after the first conversion coating, is effective to form a different conversion coating layer on the second portion of the article. Aspect 2: The conversion coating system according to Aspect 1, wherein the bismuth is present in the first conversion coating composition in a concentration of about 25 to 5000 ppm, and the organic acid is present in the first conversion coating composition in a concentration of about 50-75,000 ppm. Aspect 3: The conversion coating system according to Aspect 1 or Aspect 2, wherein second conversion coating composition comprises the zirconium in a concentration of about 50-500 ppm; free fluoride in a concentration of about 10-100 ppm; total fluoride in a concentration of about 150-2,000 ppm; and, the nitrate in a concentration of about 600-10,000 ppm. Aspect 4: The conversion coating system according to any preceding Aspect, wherein the bismuth is present in the first conversion coating composition in a concentration of about 100 to 1000 ppm. Aspect 5: The conversion coating system according to any preceding Aspect wherein the organic acid is present in the first conversion coating composition in a concentration of about 500 to 5000 ppm. Aspect 6: The conversion coating system according to any preceding Aspect,wherein the organic acid in the first conversion coating composition includes multiple carboxylic acid functionalities. Aspect 7: The conversion coating system according to any preceding Aspect, wherein the organic acid in the first conversion coating composition comprises tartaric acid. Aspect 8: The conversion coating system according to any preceding Aspect, wherein the first conversion coating composition further comprises free fluoride in a concentration up to about 5000 ppm. Aspect 9 : The conversion coating system according to any preceding Aspect, wherein the first conversion coating composition further comprises a complex fluoroacid in a concentration up to about 5000 ppm. Aspect 10: The conversion coating system according to any preceding Aspect, wherein the first conversion coating composition further comprises copper (II) ions in a concentration up to about 200 ppm. Aspect 11:The conversion coating system according to any preceding Aspect, wherein the first conversion coating composition does not include a source of phosphorus. Aspect 12:The conversion coating system according to any preceding Aspect, wherein the zirconium is present in the second conversion coating composition in a concentration of about 100-200 ppm. Aspect 13: The conversion coating system according to any preceding Aspect, wherein the zirconium in the second conversion coating composition is provided as hexafluorozirconic acid or hexafluorozirconate ions. Aspect 14:The conversion coating system according to any preceding Aspect, wherein the second conversion coating composition further comprises copper in a concentration of up to about 50 ppm. Aspect 15:The conversion coating system according to any preceding Aspect, wherein the second conversion coating composition further comprises silicon in a concentration of up to about 100 ppm.

[0010] Aspect 16: A method for conversion coating of a multi-metal article comprising: (i) contacting a multi-metal article that comprises a first portion comprising steel, galvanized steel, alloy-galvanized steel, or any combination thereof, and a second portion comprising aluminum or aluminum alloy, with a first conversion coating composition comprising bismuth and organic acid, wherein the first conversion coating composition has an acidic pH, preferably in a range of about 2.0 to about 6.0, more preferably about 2.5 to 5.5 and a temperature of at least about 10°C during operation of the system and not more than 100°C, desirably about 10-70°C, preferably about 10-54°C, for a time sufficient to form on at least one surface of the first portion of the article a bismuth-containing conversion coating layer having a coating weight of about 50- 5000 mg / m2; (ii) optionally, rinsing the multi-metal article with an aqueous rinse; and, (iii)contacting the multi-metal article with a second conversion coating composition comprising zirconium; fluoride; and, nitrate; wherein the second conversion coating composition has an acidic pH, desirably about 3.0 to 6.0, preferably about 3.5-5.0 and a temperature of at least about 10°C during operation of the system and not more than 100°C, desirably about 20-65°C, preferably about 20-54°C, for a time sufficient to form on at least one surface of the second portion of the multi-metal article a zirconium-containing conversion coating layer having a coating weight of about 10 to 200 mg / m2. Aspect 17: The method according to any one of the foregoing method Aspects, wherein the bismuth is present in the first conversion coating composition in a concentration of about 25 to 5000 ppm, and the organic acid is present in the first conversion coating composition in a concentration of about 50-75,000 ppm. Aspect 18: The method according to any one of the foregoing method Aspects, wherein second conversion coating composition comprises the zirconium in a concentration of about 50-500 ppm; free fluoride in a concentration of about 10-100 ppm; total fluoride in a concentration of about 150- 2,000 ppm; and, the nitrate in a concentration of about 600-10,000 ppm. Aspect 19: The method according to any one of the foregoing method Aspects, wherein the bismuth is present in the first conversion coating composition in a concentration of about 100 to 1000 ppm. Aspect 20: The method according to any one of the foregoing method Aspects, wherein the organic acid is present in the first conversion coating composition in a concentration of about 500 to 5000 ppm. Aspect 21: The method according to any one of the foregoing method Aspects, wherein the organic acid in the first conversion coating composition includes multiple carboxylic acid functionalities. Aspect 22: The method according to any one of the foregoing method Aspects, wherein the organic acid in the first conversion coating composition comprises tartaric acid. Aspect 23: The method according to any one of the foregoing method Aspects, wherein the first conversion coating composition further comprises free fluoride in a concentration up to about 5000 ppm. Aspect 24: The method according to any one of the foregoing method Aspects, wherein the first conversion coating composition further comprises a complex fluoroacid in a concentration up to about 5000 ppm. Aspect 25: The method according to any one of the foregoing method Aspects, wherein the first conversion coating composition further comprises copper (II) ions in a concentration up to about 200 ppm. Aspect 26: The method according to any one of the foregoing method Aspects, wherein the first conversion coating composition does not include a source of phosphorus. Aspect 27: The method according to any one of theforegoing method Aspects, wherein the zirconium is present in the second conversion coating composition in a concentration of about 100-200 ppm. Aspect 28: The method according to any one of the foregoing method Aspects, wherein the zirconium in the second conversion coating composition is provided as hexafluorozirconic acid or hexafluorozirconate ions. Aspect 29: The method according to any one of the foregoing method Aspects, wherein the second conversion coating composition further comprises copper in a concentration of up to about 50 ppm. Aspect 30: The method according to any one of the foregoing method Aspects, wherein the first conversion coating composition and the second conversion coating composition each individually contacts the multi-metal article by immersing the multi-metal article, by spraying, or any combination thereof, preferably in the absence of applied electromotive force. Aspect 31: The method according to any one of the foregoing method Aspects, wherein the article is contacted with the first conversion coating composition for about 10 seconds to about 30 minutes. Aspect 32: The method according to any one of the foregoing method Aspects, wherein the article is contacted with the second conversion coating composition for about 20 seconds to about 20 minutes. Aspect 33: The method according to any one of the foregoing method Aspects, further comprising rinsing the article after contacting the article with the second conversion coating composition. Aspect 34: The method according to any one of the foregoing method Aspects, further comprising contacting the article with a sealer composition after contacting the article with the second conversion coating composition. Aspect 35: The method according to any one of the foregoing method Aspects, further comprising electrophoretically painting the article after contacting the article with the second conversion coating composition. Aspect 36: The method according to any one of the foregoing method Aspects, wherein the second conversion coating composition further comprises silicon in a concentration of up to about 100 ppm.

[0011] Aspect 37: A multi-metal article comprising (i) a zinciferous or ferrous surface with an adherent first conversion coating layer comprising bismuth deposited on the zinciferous or ferrous surface, and (ii) an aluminum or aluminum alloy surface with a second conversion coating layer comprising ZrO2on the aluminum or aluminum alloy surface, wherein the first conversion coating layer and the second conversion coating layer were produced by the method according to any one of the foregoing method Aspects. Aspect 38: A multi-metal article comprising: a first portion comprising a zinciferous or ferrous surface and a first conversioncoating layer on the zinciferous or ferrous surface, the first conversion coating layer comprising bismuth, a bismuth compound, or both in an amount of about 50 to 5000 mg / m2; and, a second portion comprising an aluminum or aluminum alloy surface and a second conversion coating layer on the aluminum or aluminum alloy surface, the second conversion coating layer comprising ZrO2. Aspect 39: The multi-metal article according to Aspect 38, wherein the bismuth or bismuth compound comprises elemental bismuth, bismuth oxide, bismuth hydroxides, or a combination thereof. Aspect 40: The multi-metal article according to Aspect 38 or Aspect 39, wherein the first conversion coating layer further comprises O, C, Cu, iron, zinc, or aluminum from at least the first portion of the multi-metal article, or any combination thereof. Aspect 41: The multi-metal article according to any one of Aspects 38-40, wherein the first conversion coating layer comprises Zr in an amount of about 5 to 100 mg / m2. Aspect 42: The multi-metal article according to any one of Aspects 38-41, further comprising an electrophoretic paint coating on the first and second conversion coating layers. Aspect 43: The multi-metal article according to Aspect 42, wherein the electrophoretic paint coating on the first conversion coating layer has a thickness that is substantially the same as a thickness of the electrophoretic paint coating on the second conversion coating layer. Aspect 44: The multi- metal article according to Aspect 42 or Aspect 43, wherein no mapping defects are exhibited between the electrophoretic paint coating on the first conversion coating layer and the electrophoretic paint coating on the second conversion coating layer. Aspect 45: The multi- metal article according to any one of Aspects 42-44, wherein the electrophoretic paint coating on the first conversion coating layer is substantially visually indistinguishable from the electrophoretic paint coating on the second conversion coating layer. Aspect 46: The multi- metal article according to any one of Aspects 42-45, wherein the electrophoretic paint coating on both the first and second conversion coating layers has an adhesion characterized by at least 95% of the electrophoretic paint coating remaining following soaking of the article for 48 hours in water as measured according to GMW14829 / 14704. Aspect 47: The multi-metal article according to any one of Aspects 38-46, wherein the first conversion coating layer and the second conversion coating layer each have a corrosion resistance characterized by a scribe creep of about 2.5 to 6 mm as measured according to GMW14872.DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0012] The present invention may be understood more readily by reference to the following detailed description taken in connection with the accompanying examples, which form a part of this disclosure. It is to be understood that this invention is not limited to the specific products, methods, conditions or parameters described and / or shown herein, and that the terminology used herein is for the purpose of describing particular embodiments by way of example only and is not intended to be limiting of the claimed invention.

[0013] The disclosures of each patent, patent application, and publication cited or described in this document are hereby incorporated herein by reference, in their entirety.

[0014] As employed above and throughout the disclosure, the following terms and abbreviations, unless otherwise indicated, shall be understood to have the following meanings.

[0015] In the present disclosure the singular forms “a”, “an”, and “the” include the plural reference, and reference to a particular numerical value includes at least that particular value, unless the context clearly indicates otherwise. Thus, for example, a reference to “a compound” is a reference to one or more of such compounds and equivalents thereof known to those skilled in the art, and so forth. Furthermore, when indicating that a certain chemical moiety “may be” X, Y, or Z, it is not necessarily intended by such usage to exclude other choices for the moiety; for example, a statement to the effect that a moiety “may be alkyl, aryl, or amino” does not necessarily exclude other choices for the moiety, such as halo, aralkyl, and the like.

[0016] When values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. As used herein, “about X” (where X is a numerical value) preferably refers to ±10% of the recited value, inclusive. For example, the phrase “about 8” may refer to a value of 7.2 to 8.8, inclusive; as another example, the phrase “about 8%” may refer to a value of 7.2% to 8.8%, inclusive. Also, when the term “about” precedes a range, it is understood that the term modifies both recited endpoints and all points embraced within the range. For example, the phrase “about 1-10” is understood to mean “about 1 to about 10”, as well as “about x”, wherein x refers to any value between 1 and 10. Where present, all ranges are inclusive and combinable. For example, when a range of “1 to 5” is recited, the recited range should be construed as including ranges “1 to 4”, “1 to 3”, “1-2”, “1- 2 & 4-5”, “1-3 & 5”, and the like. In addition, when a list of alternatives is positively provided,such listing can be interpreted to mean that any of the alternatives may be excluded, e.g., by a negative limitation in the claims. For example, when a range of “1 to 5” is recited, the recited range may be construed as including situations whereby any of 1, 2, 3, 4, or 5 are negatively excluded; thus, a recitation of “1 to 5” may be construed as “1 and 3-5, but not 2”, or simply “wherein 2 is not included.” In another example, when a listing of possible choices for a moiety including “hydrogen, alkyl, and aryl” is provided, the recited listing may be construed as including situations whereby any of hydrogen, alkyl, and aryl is negatively excluded; thus, a recitation of “hydrogen, alkyl, and aryl” may be construed as “hydrogen and aryl, but not alkyl”, or simply “wherein the moiety is not alkyl”.

[0017] As used herein, a “conversion coating composition” represents the wet chemistry that reacts with a metal surface to form a conversion coating.

[0018] A “conversion coating” is a layer or film bonded to a metal surface, deposited by reaction of the conversion coating composition with the metal surface. The conversion coating generally comprises chemical elements from the metal surface, the conversion coating composition, and reaction products thereof.

[0019] Throughout the description, unless expressly stated to the contrary: percent, “parts of”, and ratio values are by weight or mass; molecular weight (MW) is weight average molecular weight unless otherwise specified; the word “mole” means “gram mole”, and the word itself and all of its grammatical variations may be used for any chemical species defined by all of the types and numbers of atoms present in it, irrespective of whether the species is ionic, neutral, unstable, hypothetical or in fact a stable neutral substance with well-defined molecules.

[0020] As described above, traditional tri-cationic zinc phosphate conversion coating systems contain undesirable heavy metals, generate solid waste via precipitation of sludge, and contain a high concentration of phosphate ion that can contribute to eutrophication, e.g., over enrichment of natural water supplies due to influx of phosphate nutrients, causing ecosystem damage resulting in algal blooms. The phosphate baths also operate at elevated temperature requiring increased energy usage.

[0021] Several zirconium oxide conversion coating technologies were developed to replace tri-cationic zinc phosphate. In general, however, these thin film zirconium oxide technologies do not provide corrosion resistance on steel substrates equal to zinc phosphate in every corrosive environment. Some automotive OEM manufacturers have adopted zirconiumoxide conversion coating technologies for certain applications. The automotive OEM conversion coating market, globally, has converted about 13% of the operating lines from zinc phosphate to zirconium oxide due to performance concerns.

[0022] The presently disclosed conversion coating systems, methods, and coatings provide corrosion resistance and paint adhesion performance that improves upon zirconium oxide on multimetal substrates, and is more like that of the tri-cationic zinc phosphate while avoiding the negative aspects. The bismuth conversion coating solution does not contain any intentionally added heavy metals (none by design, e.g., no more than results from substrate etching that produces ions of Fe, Zn, or Al), does not contain intentionally added phosphate (none by design, traces may appear due to drag in or other contamination), and as such does not produce a significant amount of sludge (preferably less than 50 g / l). In particular the Bi-based coating bath produces less sludge than a similarly sized zinc phosphate conversion coating bath, with less phosphate content. The inventive coating composition is applied at a relatively low temperature, as further described herein, such that a heat exchanger is not required for the bismuth conversion coating stage. The bismuth conversion coating is an effective replacement for traditional tri-cationic zinc phosphate conversion coating systems, which contain nickel, zinc, manganese, for metal pretreatment of steel and galvanized substrates. As a second aspect of the present systems, a zirconium coating applied after the bismuth coating provides corrosion protection and paint adhesion properties to aluminum and aluminum alloy substrates. Reasonable applications include any metal substrate that is to be subsequently coated with a polymeric coating, e.g., painted and requires coating adhesion and corrosion resistance. Specific fields that can benefit may include transportation industries, automotive OEM (body-in-white), automotive components, appliance manufacture, office furniture manufacture, metal coils, metal containers, and in other industries utilizing metal substrates, in particular articles having surfaces of dissimilar metals.

[0023] Accordingly, provided herein are conversion coating systems for sequential pretreatment of an article having a first portion comprising steel, e.g. cold rolled steel (CRS), galvanized steel, or alloy-galvanized steel, and a second portion comprising aluminum or an aluminum alloy, wherein the system comprises (i) a first conversion coating bath composition comprising bismuth, for example, in a concentration of about 25 to 5000 ppm, as elemental Bi, and organic acid, for example, in a concentration of about 50-75,000 ppm, wherein the firstconversion coating composition has an acidic pH, preferably in a range of about 2.0 to about 6.0, more preferably about 2.5 to 5.5 and a temperature of at least about 10°C during operation of the system and not more than 100°C, desirably about 10-70°C, preferably about 10-54°C; and, (ii) a second conversion coating bath composition comprising zirconium, for example, in a concentration of about 50-500 ppm, as elemental Zr; free fluoride, for example, in a concentration of about 10-100 ppm; a total fluoride concentration of, for example, about 150- 2,000 ppm; and, nitrate, for example, in a concentration of about 600-10,000 ppm; wherein the second conversion coating composition has an acidic pH, desirably about 3.0 to 6.0, preferably about 3.5-5.0 and a temperature of at least about 10°C during operation of the system and not more than 100°C, desirably about 20-65°C, preferably about 20-54°C, wherein contacting the article and the first conversion coating composition is effective to form a continuous bismuth- containing conversion coating layer on the first portion of the article, and contacting the article and the second conversion coating composition, in sequence after the first conversion coating, is effective to form a different conversion coating layer on the second portion of the article.

[0024] The first and second conversion coating compositions represent solutions. However, either may include dispersed components, e.g., dispersed Bi or Zr solids, respectively, with the understanding that any dispersed components can be redissolved. In other words, in the first and second conversion coating compositions, an equilibrium between dissolved and dispersed solids is possible and reasonably expected. First Conversion Coating Step

[0025] In the first conversion coating composition, the bismuth (Bi, Bi3+) may be presented by any moiety that produces bismuth suspension or solution of bismuth ions. Nonlimiting examples include bismuth oxide, bismuth sulfate, bismuth nitrate, and bismuth subnitrate. The bismuth may be present in the first conversion coating composition in an amount of about 25 to 5000 ppm, such as 25 to 4000, 25 to 3000, 50 to 2500, 75 to 2000, 80 to 1500, or 100 to 1000 ppm, for example, in an amount of about 25, 50, 75, 100, 125, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, 2250, 2500, 2750, 3000, 3250, 3500, 3750, 4000, 4250, 4500, or 5000 ppm.

[0026] The organic acid in the first conversion coating composition can be, for example, any species with multiple carboxylic acid functionalities, such as tartaric acid, citric acid, ethylenediaminetetraacetic acid, or the like. The organic acid may represent a mixture of different species. In some embodiments, the organic acid may include a mixture of species that includes multiple species with multiple carboxylic acid functionalities, or a mixture of one or more species with multiple carboxylic acid functionalities combined with one or more monocarboxylic acids such as lactic acid, gluconic acid, gallic acid, ascorbic acid, or bicine. The organic acid may be present in the first conversion coating composition in an amount of about 50 to 75,000 ppm, such as 50 to 50,000, 100 to 25,000, 200 to 15,000, 300 to 7500, 400 to 6000, or 500 to 5000 ppm, for example, in an amount of about 50, 75, 100, 125, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, 2250, 2500, 2750, 3000, 3250, 3500, 3750, 4000, 4250, 4500, 5000, 6000, 7000, 8000, 9000, 10,000, 15,000, 20,000, 25,000, 30,000, 35,000, 40,000, 45,000, or 50,000 ppm.

[0027] The first conversion coating composition can further include free fluoride in a concentration of up to about 5000 ppm. In some embodiments, no or substantially no free fluoride is deliberately made present. In other embodiments, free fluoride is present in the first coating composition in an amount of about 1-5000 ppm, such as about 1-1000, 1-500, 1-400, 1- 300, 1-200, 1-100, 1-50, 1-40, 1-30, 1-20, 1-10, or 1-5 ppm, such as in an amount of about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 50, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1200, 1400, 1500, 1600, 1800, 2000, 2250, 2500, 3000, 3500, 4000, 4500, or 5000 ppm.

[0028] The first conversion coating composition can further include a complex fluoroacid or a salt thereof in a concentration of up to about 5000 ppm. In some embodiments, no or substantially none of a complex fluoroacid or salt is deliberately made present. In other embodiments, complex fluoroacid or salt is present in the first coating composition in an amount of about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 50, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1200, 1400, 1500, 1600, 1800, 2000, 2250, 2500, 3000, 3500, 4000, 4500, or 5000 ppm. Complex fluoroacids can include fluorosilicic acid (also referred to as hexafluorosilicic acid), hexafluorozirconic acid, hexafluorotitanic acid, and salts thereof.

[0029] The first conversion coating composition can further include copper (II) ion in a concentration of up to about 200 ppm. In some embodiments, no or substantially no copper (II)ion is deliberately made present. In other embodiments, copper (II) ion is present in the first coating composition in an amount of about 1-200 ppm, such as about 1-100, 1-90, 1-80, 1-70, 1- 60, 1-50, 1-40, 1-30, 2-30, 3-30, 4-28, or 5-25 ppm, such as in an amount of about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, or 200 ppm.

[0030] Phosphate may be present in the form of drag-in from cleaner baths and the like. In preferred embodiments, the first conversion coating composition does not include a source of phosphorus. In some embodiments, the first conversion coating composition can include phosphate (PO4) in a concentration of up to 2000 ppm, such as in an amount of about 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, or 2000 ppm.

[0031] In some embodiments, the first conversion coating composition includes nitrate (NO3) in a concentration of up to 10,000 ppm, such as about 1-10,000, 10-7500, 20-5000, 25- 4000, 50-4000, 100-3500 ppm, such as in an amount of about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 50, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1200, 1400, 1500, 1600, 1800, 2000, 2250, 2500, 3000, 3500, 4000, 4500, or 5000 ppm.

[0032] The first conversion coating composition can further include silicon (e.g., deriving from fluorosilicic acid otherwise present in the first coating composition) in a concentration of up to about 5000 ppm. In some embodiments, no or substantially no silicon is deliberately made present. In other embodiments, silicon is present in the first coating composition in an amount of about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 50, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1200, 1400, 1500, 1600, 1800, 2000, 2250, 2500, 3000, 3500, 4000, 4500, or 5000 ppm, such as about 1-5000, 1-1000, 1-750, 1-500, 1-250, 1-200, or 1-100 ppm.

[0033] The first conversion coating composition can further include one or more Group IVB metals (zirconium, titanium, or hafnium) in a total concentration of up to about 500 ppm. In some embodiments, no or substantially no Group IVB metals are deliberately made present. In other embodiments, one or more Group IVB metals are present in the first coating composition in an amount of about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 50, 100, 150, 200, 250, 300, 350, 400, 450, or 500 ppm, such as about 1-5, 1-10, 1-20, 1-30, 1-40, 1-50, 1-60, 1-70, 1-80, 1-90, 1- 100, 1-110, 1-120, 1-130, 1-140, or 1-150 ppm.

[0034] The first conversion coating composition can further include hydrogen peroxide in a concentration of up to about 1000 ppm. In some embodiments, no or substantially no hydrogen peroxide is deliberately made present. In other embodiments, hydrogen peroxide is present in the first coating composition in an amount of about 1-1000 ppm, such as about 1-1000, 1-500, 1-400, 1-300, 1-200, 1-100, 1-75, 1-70, 1-65, 1-60, 1-55, 1-50, 1-45, 1-40, 1-35, 1-30, 1- 25, 1-20, 1-15, 1-10, or 1-5 ppm, such as in an amount of about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 50, 100, 200, 300, 400, 500, 600, 700, 800, 900, or 1000 ppm.

[0035] The first conversion coating composition can further include hydroxylamine in a total concentration of up to about 500 ppm. In some embodiments, no or substantially no hydroxylamine is deliberately made present. In other embodiments, hydroxylamine is present in the first coating composition in an amount of about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 50, 100, 150, 200, 250, 300, 350, 400, 450, or 500 ppm, such as about 1-5, 1-10, 1-20, 1-30, 1-40, 1-50, 1-60, 1-70, 1-80, 1-90, 1-100, 1-110, 1-120, 1-130, 1-140, or 1-150 ppm.

[0036] The first conversion coating composition can further include sodium nitrobenzenesulfonate in a concentration of up to about 1000 ppm. In some embodiments, no or substantially no sodium nitrobenzenesulfonate is deliberately made present. In other embodiments, sodium nitrobenzenesulfonate is present in the first coating composition in an amount of about 1-1000 ppm, such as about 1-1000, 1-500, 1-400, 1-300, 1-200, 1-100, 1-75, 1- 70, 1-65, 1-60, 1-55, 1-50, 1-45, 1-40, 1-35, 1-30, 1-25, 1-20, 1-15, 1-10, or 1-5 ppm, such as in an amount of about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 50, 100, 200, 300, 400, 500, 600, 700, 800, 900, or 1000 ppm.

[0037] The first conversion coating composition can further include polyamidoamine (GAS 68410-23-1) in a total concentration of up to about 500 ppm. In some embodiments, no or substantially no polyamidoamine is deliberately made present. In other embodiments, polyamidoamine is present in the first coating composition in an amount of about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 50, 100, 150, 200, 250, 300, 350, 400, 450, or 500 ppm, such as about 1-5, 1-10, 1-20, 1-30, 1-40, 1-50, 1-60, 1-70, 1-80, 1-90, 1-100, 1-110, 1-120, 1-130, 1-140, or 1-150 ppm.

[0038] The first conversion coating composition can further include phenalkamine in a total concentration of up to about 500 ppm. In some embodiments, no or substantially no phenalkamine is deliberately made present. In other embodiments, phenalkamine is present inthe first coating composition in an amount of about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 50, 100, 150, 200, 250, 300, 350, 400, 450, or 500 ppm, such as about 1-5, 1-10, 1-20, 1-30, 1-40, 1-50, 1-60, 1-70, 1-80, 1-90, 1-100, 1-110, 1-120, 1-130, 1-140, or 1-150 ppm.

[0039] The first conversion coating composition can further include dopamine / polyethyleneimine (PEI) polymer in a total concentration of up to about 500 ppm. In some embodiments, no or substantially no dopamine / polyethyleneimine polymer is deliberately made present. In other embodiments, dopamine / polyethyleneimine polymer is present in the first coating composition in an amount of about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 50, 100, 150, 200, 250, 300, 350, 400, 450, or 500 ppm, such as about 1-5, 1-10, 1-20, 1-30, 1-40, 1-50, 1-60, 1-70, 1-80, 1-90, 1-100, 1-110, 1-120, 1-130, 1-140, or 1-150 ppm.

[0040] The first conversion coating composition has an acidic pH and may have a pH of about 2-6, such as a pH of 2-5.5, 2.5-5.5, 3-5.5, or 3-5, such as 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.64.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, or 5.5. The temperature of the first conversion coating composition is preferably at least 10°C during operation of the system and not more than 100°C, preferably at about 10-60°C, 15- 60°C, 10-55°C, 15-55°C, 20-60°C, or 20-55°C, such as at about 10, 15, 20, 25, 30, 35, 40, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, or 60°C. Higher temperatures than 60°C may be used, but are not required and require more energy to be maintained.

[0041] The present systems may be arranged such that the duration of time of the application of the first conversion coating to a surface of the article is from about 10 seconds to about 30 minutes. Exemplary application times include about 10, 20, 30, 40, 50, 60, 70, 80, or 90 seconds, or about 1.5, 1.75, 2, 2.25, 2.5, 2.75, 3, 3.25, 3.5, 3.75, 4, 4.25, 4.5.4.75, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30 minutes. Second Conversion Coating Step

[0042] The second conversion coating compositions contain zirconium. The zirconium may be provided as hexafluorozirconic acid or hexafluorozirconate ions. Alternative or additional sources of zirconium can include other water soluble sources of zirconium such as zirconyl nitrate or zirconium nitrate provided that they do not unduly interfere with the objects of the invention in producing a multi-metal article having adequate conversion coating coverage on the metal surfaces. The concentration of zirconium in the second conversion coatingcompositions may be from about 50-500 ppm, measured as elemental Zr. For example, zirconium may be present in the second coating composition in an amount of about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 50, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 250, 300, 350, 400, 450, or 500 ppm, such as about 1-5, 1-10, 1-20, 1-30, 5-40, 10-50, 10-60, 20-70, 20-80, 30-90, 40-100, 50-110, 60-120, 70-130, 80-140, 80-150, 85-160, 90-170, 90-180, 95-190, or 100-200 ppm.

[0043] The second conversion coating compositions may optionally contain copper. The concentration of zirconium in the second conversion coating compositions may be up to about 50 ppm. For example, copper may be present in the second coating composition in an amount of about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 20, 25, 30, 35, 40, 45, or 50 ppm, such as about 1-5, 1-10, 1-20, 5-20, 10-20, 1-30, 5-30, 10-30, 5-40, 10-40, 5-50, or 10-50 ppm.

[0044] The second conversion coating compositions may optionally contain silicon. The silicon may be provided as colloidal silicon, for example. The concentration of silicon in the second conversion coating compositions may be up to about 100 ppm. For example, silicon may be present in the second coating composition in an amount of about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100 ppm, such as about 1-5, 1-10, 5-10, 1-20, 5-20, 6-20, 8-20, 10-20, 1-30, 5-30, 10-30, 5-40, 10-40, 5-50, 8- 50, or 10-50 ppm.

[0045] The second conversion coating compositions have a free fluoride concentration of about 10-200 ppm. For example, free fluoride may be present in the second coating composition in an amount of about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 110, 112, 114, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, 180, 185, 190, 195 ppm or 200 ppm, such as about 1-5, 1-10, 5-10, 1-20, 5-20, 6-20, 8-20, 10-20, 1-30, 5-30, 10-30, 15-30, 1-40, 5-40, 10-40, 15-40, 5-50, 8- 50, 10-50, 15-50, or 20-50 ppm.

[0046] The second conversion coating compositions have a total fluoride concentration of about 150-2000 ppm. For example, the total fluoride concentration in the second coating composition may be about 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, or 2000 ppm, such as about 200-2000, 300-2000, 400-1900, 500-1800, 500-1700, 550-1600, 600-1500, 600-1600, 700-1700, 800-1700, 900-1800, or 1000-2000 ppm.

[0047] The second conversion coating composition includes nitrate (NO3-1) in a concentration of about 600-10,000 ppm, such as about 800-10,000, 900-9000, 1000-8000, 1500- 8000, 2000-7500, 2500-7000, 3000-7000, or 3500-6500, for example, in an amount of about 600, 700, 800, 900, 1000, 1200, 1400, 1500, 1600, 1800, 2000, 2250, 2500, 3000, 3500, 4000, 4500, 5000, 5500, 6000, 6500, 7000, 7500, 8000, 8500, 9000, 9500, or 10,000 ppm.

[0048] The second conversion coating composition has an acidic pH, desirably about 3.0-6.0 and may have a pH of about 3.5-5, such as a pH of 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, or 5.0. The temperature of the second conversion coating composition is at least 10°C, preferably at least 15°C during operation of the system and not more than 100°C, preferably at about 10-60°C, 15-60°C, 10-55°C, 15-55°C, 20- 60°C, 20-55°C, 20-54°C, 25-50°C, 25-45°C, or 25-40°C, such as at about 15, 20, 25, 30, 35, 40, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, or 60°C. Higher temperatures than 60°C may be used, but are not required and require more energy to be maintained.

[0049] The present systems may be arranged such that the duration of time of the application of the second conversion coating to a surface of the article is from about 20 seconds to about 20 minutes. Exemplary application times include about 20, 30, 40, 50, 60, 70, 80, or 90 seconds, or about 1.5, 1.75, 2, 2.25, 2.5, 2.75, 3, 3.25, 3.5, 3.75, 4, 4.25, 4.5.4.75, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 minutes.

[0050] In accordance with the present systems, contacting the article and the first conversion coating composition is effective to form a bismuth-containing conversion coating layer on the first portion of the article, and contacting the article and the second conversion coating composition, sequentially after the first conversion coating, is effective to form a different conversion coating layer on the second portion of the article, without removing or significantly etching the first conversion coating layer. In other words, a bismuth-containing conversion coating layer is formed on the steel, galvanized steel, or alloy-galvanized steel of the first portion of the article, and a different coating layer (comprising ZrO2) is formed on the aluminum or aluminum alloy of the second portion of the article. To the extent that material deriving from the first (bismuth) conversion coating composition forms on the second (aluminum) portions of the article, such material does not represent a functional conversion coating layer that would be in addition to the layer that forms on the aluminum portions from the second conversion coating composition. The present systems therefore account for thedifferentially constituted surfaces of the multi-metal article in order to produce uniform, contiguous conversion coating layers with excellent corrosion resistance and paint adhesion (e.g., as compared with conventional commercial pre-treatment comprising tri-cationic zinc phosphate) on both surface types. The inventive systems provide the conversion coatings without the use of added heavy metals, preferably without phosphorus, and under reduced operating temperatures.

[0051] As noted, in certain embodiments, the first and / or second conversion coating compositions do not include a source of phosphorus. Accordingly, the present compositions may be substantially phosphorus-free, meaning that the compositions do not include phosphorus in an amount exceeding trace quantities that are incidentally present deriving from one or more of the materials that are intentionally included in the composition. For example, at least some embodiments according to the 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 percent, more preferably said numerical values in grams per liter, more preferably said numerical values in ppm, of phosphorus.

[0052] For a variety of reasons, it is preferred that inventions disclosed herein (e.g., systems, methods and articles of manufacture) may be made in the absence of certain ingredients, and, i.e., be free of certain materials whether added or generated in situ other than minor amounts of contaminants, or may be free or substantially free from many ingredients used in compositions for similar purposes in the prior art. Specifically, it is increasingly preferred in the order given, independently for each preferably minimized ingredient listed below, that at least some embodiments the first and / or second conversion coating compositions do not include or may 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 percent, more preferably said numerical values in grams per liter, most preferably said numerical values in ppm, of each of the following constituents: silane and / or siloxane-based materials, epoxy resin, including bisphenol-based resins, PFAS; waxes, whether from plants, animals, or mineral origin, e.g. carnauba wax, beeswax, Montan wax, petrochemical-based waxes, synthetic waxes, or esters of long-chain fatty acids with long-chain monohydric alcohols; oxidizing agents such as peroxyacids, permanganate, perchlorate, chlorate, chlorite, hypochlorite, perborate, hexavalent chromium, trivalent chromium, sulfuric acid and sulfate, as well as formaldehyde, formamide, hydroxylamines, cyanides, cyanates; rare earth elements, e.g., scandium, yttrium, and the lanthanide series of elements: lanthanum, cerium, praseodymium, neodymium,samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium thulium, ytterbium and lutetium; boron, e.g., borax, borate; strontium; free chloride, bromide or iodide; or a combination thereof.

[0053] The present disclosure also provides methods for conversion coating of a multi- metal article comprising (i) contacting a multi-metal article that comprises a first portion comprising steel, galvanized steel, alloy-galvanized steel, or any combination thereof, and a second portion comprising aluminum or aluminum alloy, with a first conversion coating composition comprising bismuth in a concentration of about 25 to 5000 ppm, and organic acid in a concentration of about 50-75,000 ppm, wherein the first conversion coating composition has an acidic pH, preferably in a range of about 2.0 to about 6.0, more preferably about 2.5 to 5.5 and a temperature of at least about 10°C during operation of the system and not more than 100°C, desirably about 10-70°C, preferably about 10-54°C, for a time sufficient to form on at least one surface of the first portion of the article a bismuth-containing conversion coating layer having a coating weight of about 50-5000 mg / m2, which coating weight is indicated as the mass of elemental Bi present therein as determined via X-ray fluorescence; (ii) optionally, rinsing the multi-metal article with an aqueous rinse; and, (iii) contacting the multi-metal article with a second conversion coating composition comprising zirconium in a concentration of about 50-500 ppm; free fluoride in a concentration of about 10-100 ppm; a total fluoride concentration of about 150-2,000 ppm; and, nitrate in a concentration of about 600-10,000 ppm; wherein the second conversion coating composition has an acidic pH, desirably about 3.0 to 6.0, preferably about 3.5-5.0 and a temperature of at least about 10°C during operation of the system and not more than 100°C, desirably about 20-65°C, preferably about 20-54°C, for a time sufficient to form on at least one surface of the second portion of the multi-metal article a zirconium-containing conversion coating layer having a coating weight of about 10 to 200 mg / m2, which coating weight is indicated as the mass of elemental Zr present therein as determined via X-ray fluorescence.

[0054] The multi-metal article may be any component, device, or mechanism that includes a first portion and a second portion respectively comprising the metals identified supra, and that is to be painted and requires paint adhesion and corrosion resistance. The first portion can include ferrous, zinc coated ferrous (e.g., hot-dipped galvanized steel or electrogalvanizedsteel), or zinciferous alloys. It is noted that magnesium alloys may also be coated by the step of contacting with the second conversion coating composition. Exemplary multi-metal articles include automotive body in white, automotive components, metal containers, furniture, metal coil, and the like.

[0055] The characteristics of the first conversion coating composition of the present methods may be in accordance with any of the embodiments described in the present disclosure in connection with the inventive systems for sequential pretreatment. Likewise, the operating conditions under which the step of contacting the article with the first conversion coating composition, including pH, temperature, and contacting time may be in accordance with any of the embodiments described supra in connection with the inventive systems. The first conversion coating composition can contact the multi-metal article by immersing the multi-metal article, spraying, or a combination thereof, preferably in the absence of an applied electromotive force. The specified contacting times and other conditions are sufficient to form on at least one surface of the first portion of the article a bismuth-containing conversion coating layer having a coating weight of about 50-5000 mg / m2, such as a coating weight of about 50, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, 2100, 2200, 2300, 2400, 2500, 2600, 2700, 2800, 2900, 3000, 3100, 3200, 3300, 3400, 3500, 3600, 3700, 3800, 3900, 4000, 4100, 4200, 4300, 4400, 4500, 4600, 4700, 4800, 4900, or 5000 mg / m2.

[0056] Characteristics of the second conversion coating composition of the present methods may be in accordance with any of the embodiments described in the present disclosure in connection with the inventive systems, and the operating conditions under which the step of contacting the article with the second conversion coating composition, including pH, temperature, and contacting time may be in accordance with any of the embodiments described supra in connection with the inventive systems. The second conversion coating composition can contact the multi-metal article by immersing the multi-metal article, spraying, or a combination thereof, preferably in the absence of an applied electromotive force. The specified contacting times and other conditions are sufficient to form on at least one surface of the first portion of the article a zirconium-containing conversion coating layer having a coating weight of about 10-200 mg / m2, such as a coating weight of about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, 180, 185, 190, 195, or 200 mg / m2.

[0057] The step of contacting the article with the second conversion coating composition does not disrupt the coating that is produced by contacting the article with the first conversion coating composition. For example, in certain embodiments, the step of contacting the article with the second conversion coating does not dissolve more than about 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, or 5% of the conversion coating layer that is formed on the steel, galvanized steel, or alloy-galvanized steel surfaces of the article by contacting such surfaces with the first conversion coating composition.

[0058] In some embodiments, particularly with multi-metal substrates, aluminum substrates contacted with the first conversion coating step tends to result in a range of less than 50 mg / m2deposition of adherent Bi coating on the aluminum / aluminum alloy surfaces, measured as elemental Bi. In some embodiments, the first conversion coating bath may form discontinuous areas of Bi-containing coating deposition, optionally being sites for precipitation or coating initiation by the second conversion coating onto the aluminum / aluminum alloy surfaces.

[0059] In some embodiments, contact of zinciferous and / or ferrous metal surfaces having a layer of the Bi conversion coating deposited thereon with the Zr containing conversion coating composition of the second step may result in deposition of Zr containing materials on the Bi-based coating. Generally, Zr may be present, if at all, in amounts of up to 20 mg / m2, measured as elemental Zr on / in the Bi-based coating.

[0060] The present methods may comprise a further step of rinsing the multi-metal article after contacting the article with the conversion coating composition. When performed, rinsing of the article may be performed using water, such as deionized (DI) water.

[0061] The presently disclosed methods may optionally comprise an additional step of contacting the multi-metal article with a sealer composition after contacting the article with the second conversion coating composition. Compositions for sealing a conversion coated article, e.g., prior to painting, include, for example, chromate rinses, reactive or non-reactive organic polymers and other treatments commercially available under the Bonderite M or M-PT tradenames. In a preferred embodiment, a polymeric post-treatment is applied after the second stage.

[0062] Following the step of contacting the article with the second conversion coating composition, the article may be electrophoretically painted. If the article is subjected to a rinsingand / or sealing step as described above, electrophoretic painting should be subsequent to such step(s).

[0063] Also provided herein are multi-metal articles comprising (i) a zinciferous or ferrous surface with an adherent first conversion coating layer comprising bismuth deposited on the zinciferous or ferrous surface, and (ii) an aluminum or aluminum alloy surface with a second conversion coating layer comprising ZrO2on the aluminum or aluminum alloy surface, wherein the first conversion coating layer and the second conversion coating layer were produced by a presently disclosed method for conversion coating.

[0064] The present disclosure also provides multi-metal articles comprising a first portion comprising a zinciferous or ferrous surface and a first conversion coating layer on the zinciferous or ferrous surface, the first conversion coating comprising bismuth, a bismuth compound, or both in an amount of about 50 to 5000 mg / m2; and, a second portion comprising an aluminum or aluminum alloy surface and a second conversion coating on the aluminum or aluminum alloy surface, the second conversion coating comprising ZrO2.

[0065] As noted, the portions of the multi-metal articles with an adherent first conversion coating layer can include ferrous, zinc coated ferrous, or zinciferous alloys. Such portions can also include zinc coated alloys (e.g., hot-dipped galvanized steel or electrogalvanized steel).

[0066] In the first conversion coating, the bismuth or bismuth compound may comprise, for example, elemental bismuth, bismuth oxide, bismuth hydroxides, or a combination thereof. The amount of bismuth in the first conversion coating layer may be about 50 to 5000 mg / m2, such as about 50-1000, 75-750, 100-500, 150-350, 200-300, or 200-260 mg / m2. For example, bismuth may be present in the first conversion coating layer in an amount of about 50, 75, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300, 310, 320, 330, 340, 350, 360, 370, 380, 390, 400, 450, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, 2250, 2500, 2750, 3000, 3250, 3500, 3750, 4000, 4250, 4500, 4750, or 5000 mg / m2.

[0067] The first conversion coating layer may further comprise one or more of oxygen, carbon, copper, iron, zinc, zirconium, or aluminum from at least the first portion of the multi- metal article, or any combination thereof. In other words, such elements may not be intentionally included in the conversion coating composition that is used to form the firstconversion coating layer, but become present in the layer from surrounding sources, for example, due to etching of the article substrate during the conversion coating process, or from the second conversion coating layer.

[0068] When present, the iron, measured as elemental Fe by means known in the art, e.g., GDOES, can be in the first conversion coating layer in an amount of up to 25% by weight, based on the total weight of the first conversion coating layer when the first conversion coating layer is on a steel or galvanized substrate. For example, iron may be present in the first coating layer in an amount of about 0.25, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 wt.%.

[0069] When present, the zinc, measured as elemental Zn by means known in the art, e.g., GDOES, can be in the first conversion coating layer in an amount of up to 30% by weight, based on the total weight of the first conversion coating layer when the first conversion coating layer is on a galvanized substrate. For example, zinc may be present in the first coating layer in an amount of about 0.25, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30 wt.%, based on the total weight of the first conversion coating layer.

[0070] Traces of aluminum, due to etching of aluminum substrates passing through the process, may be incorporated into the first conversion coating layer, i.e., Bi-containing coating.

[0071] The multi-metal articles according to the present disclosure may further comprise an electrophoretic paint coating on the first and second conversion coating layers. As described herein, the present conversion coatings have excellent paint adhesion properties that are at least comparable to those of traditional tri-cationic zinc phosphate compositions. For example, in some embodiments, the electrophoretic paint coating on both the first and second conversion coating layers has an adhesion characterized by at least 95% of the electrophoretic paint coating remaining following soaking of the article for 48 hours in water as measured according to GMW14829 / 14704. Additionally or alternatively, the first conversion coating layer and the second conversion coating layer may each have a corrosion resistance characterized by a scribe creep of about 2.5 to 6 mm as measured according to GMW14872.

[0072] Furthermore, the first and second conversion coatings can enable an electrophoretic paint coating that is substantially uniform across the respective coatings. For example, the electrophoretic paint coating on the first conversion coating layer may have athickness that is substantially the same as the thickness of the electrophoretic paint coating on the second version coating layer, desirably thickness may vary less than 15%, 10% or 5%. In certain embodiments, no or substantially no mapping defects are exhibited between the electrophoretic paint coating on the first conversion coating layer and the electrophoretic paint coating on the second conversion coating layer. Mapping defects are understood in the surface coating arts as areas of painted surface with a differing texture or degree of gloss, often exhibiting defined boundary or contour lines. In some embodiments, the electrophoretic paint coating on the first conversion coating layer is substantially visually indistinguishable from the electrophoretic paint coating on the second conversion coating layer, i.e. the electrophoretic paint coatings on the first and second conversion layers look the same upon unaided visual inspection. Examples

[0073] The present invention is further defined in the following Examples. It should be understood that these examples, while indicating preferred embodiments of the invention, are given by way of illustration only, and should not be construed as limiting the appended claims. From the above discussion and these examples, one skilled in the art can ascertain the essential characteristics of this invention, and without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions. Example 1 – Conversion Coating

[0074] A first conversion coating solution was prepared as follows: DI water 89.90% (weight)

[0075] pH was increased using a 10% ammonium bicarbonate solution (Bonderite M- AD 700) until pH=3.5. This resulted in a slight blue / green solution containing 500ppm Bi, 10ppm Cu, 1000ppm fluorosilicic acid, 2000ppm tartaric acid. This mixture also contained some undissolved bismuth subnitrate (white solids). The solution was warmed to 90°F. Aluminum nitrate solution was added until the Free F concentration = 10ppm & pH was adjusted to 4.0 using a 10% ammonium bicarbonate solution. The specific stepwise conversion coating process using the bismuth conversion coating solution is as follows: •Bonderite C-AK T51(2%v / v, 120F, FAik 5.0, 90 second spray, 10psi)• Rinse: City Water (100F, 60 second spray, 10psi) • Rinse: DI Water (70F, 60 second spray, 10psi) • Bi - Conversion Coating: 90F, 120 seconds immersion • Rinse: DI Water (70F, 60 seconds spray, 10psi) • Zr - Conversion Coating: 90F, 60 seconds immersion • Rinse: DI Water (70F, 60 seconds spray, 10psi) • E-coat: BASF CathoGuard 800 (95 °F, 240 second immersion, 0.9Amps constant current ~230V) • Rinse: DI Water (75F, 60 seconds spray, 10psi) • Paint Cure: Oven bake (365F, 35 minutes)

[0076] A second, zirconium conversion coating solution was prepared containing fluorozirconic acid, copper (II) nitrate, silica, nitrate, fluoride, & ammonium ion where Zr=150ppm; Cu=20ppm; NO3=4500ppm; SiO2=20ppm; Free F=20ppm; pH=4.2.

[0077] ACT cold rolled steel (CRS), electro-galvanized steel (EG), hot dipped galvanized steel (HDG), and Al6111 (aluminum alloy) panels were dipped into the coating solutions (process outlined below). This resulted in a visibly black coatings on each substrate except Al6111. Coatings on CRS, EG, HDG contained the elements Bi, O, C, Cu, Fe, Zn from the base substrates with Bi = 200-260 mg / m2as determined via XRF. Al6111 substrate contained Al, Zr, and O, with Zr = 56 mg / m2as determined via XRF, and a trace amount of Bi ranging from 0 to 30 mg / m2as determined via XRF.Example 2 – Painting of Conversion Coated Surfaces

[0078] After the application of conversion coating as described in Example 1, panels were painted with cathodic electrocoat, BASF CathoGuard 800, without drying or stoppage in the process. The E-coat process is described below. Paint application time = 4.0 minutes.

[0079] Standard tri-cationic zinc phosphate, Bonderite M-ZN 958, panels were E- coated with BASF CathoGuard 800 using the same paint application parameters. E-coat dry- film-thickness was measured via Elcometer coating thickness gauge based on electromagnetic induction as is known in the art.

[0080] Results. E-coat appearance was smooth, uniform without mapping defects. Bismuth coating were visibly darker in color than the Bonderite M-ZN 958 control panels. E- coat dry-film-thickness was comparable between the bismuth / zirconium coatings and Bonderite M-ZN 958 controls: Dry-film-thickness in mils (1 mil = 1 / 1000 inch = 0.0254 mm) ) )includes initial cross-hatch, 24 hour water soak followed by cross-hatch, and 48 hour water soak followed by cross-hatch. Each cross-hatch is followed by tape-pull defined by the General Motors test methods. Panels were tested in triplicate. Results are shown below. Paint Adhesion, % Paint Remaining After Tape Pull rEG Bonderite M-ZN 958 100 100 100 The painfore comparable to the zinc phosphate control. Example 3 – Corrosion Resistance of Inventive Conversion Coatings

[0082] Cyclic corrosion performance was evaluated using GMW14872, Exposure C (29 cycles, Mass loss = 4.026g). The test cycle is defined by the General Motors test method. Panels were tested in triplicate. Ref. At2020-0849. Corrosion Results – Scribe Creep (mm) The corrosions was therefore comparable to the zinc phosphate control.

Claims

CLAIMS What is claimed:

1. A conversion coating system for sequential pretreatment of an article having a first portion comprising steel, galvanized steel, or alloy-galvanized steel, and a second portion comprising aluminum or an aluminum alloy, the system comprising: (i) a first conversion coating composition comprising dissolved and / or dispersed bismuth, and organic acid, wherein the first conversion coating composition has an acidic pH, desirably about 2.0 to 6.0, preferably about 2.5 to 5.5 and a temperature of at least about 10°C during operation of the system and not more than 100°C; and, (ii) a second conversion coating composition comprising zirconium; fluoride; and, nitrate; wherein the second conversion coating composition has an acidic pH, desirably about 3.0 to 6.0, preferably about 3.5-5.0 and a temperature of at least about 10°C during operation of the system and not more than 100°C, desirably about 20-65°C, preferably about 20-54°C, during operation of the system and not more than 100°C; wherein contacting the article and the first conversion coating composition is effective to form a bismuth- containing conversion coating layer on the first portion of the article, and contacting the article and the second conversion coating composition, in sequence after the first conversion coating, is effective to form a different conversion coating layer on the second portion of the article.

2. The conversion coating system according to claim 1, wherein the bismuth is present in the first conversion coating composition in a concentration of about 25 to 5000 ppm, and the organic acid is present in the first conversion coating composition in a concentration of about 50- 75,000 ppm.

3. The conversion coating system according to claim 1, wherein second conversion coating composition comprises the zirconium in a concentration of about 50-500 ppm; free fluoride in a concentration of about 10-100 ppm; total fluoride in a concentration of about 150-2,000 ppm; and, the nitrate in a concentration of about 600-10,000 ppm.

4. The conversion coating system according to claim 1, wherein the bismuth is present in the first conversion coating composition in a concentration of about 100 to 1000 ppm.

5. The conversion coating system according to claim 1, wherein the organic acid is present in the first conversion coating composition in a concentration of about 500 to 5000 ppm.

6. The conversion coating system according to claim 1, wherein the organic acid in the first conversion coating composition includes multiple carboxylic acid functionalities.

7. The conversion coating system according to claim 1, wherein the organic acid in the first conversion coating composition comprises tartaric acid.

8. The conversion coating system according to claim 1, wherein the first conversion coating composition further comprises free fluoride in a concentration up to about 5000 ppm.

9. The conversion coating system according to claim 1, wherein the first conversion coating composition further comprises a complex fluoroacid in a concentration up to about 5000 ppm.

10. The conversion coating system according to claim 1, wherein the first conversion coating composition further comprises copper (II) ions in a concentration up to about 200 ppm.

11. The conversion coating system according to claim 1, wherein the second conversion coating composition further comprises silicon in a concentration of up to about 100 ppm.

12. The conversion coating system according to claim 1, wherein the zirconium is present in the second conversion coating composition in a concentration of about 100-200 ppm.

13. The conversion coating system according to claim 1, wherein the zirconium in the second conversion coating composition is provided as hexafluorozirconic acid or hexafluorozirconate ions.

14. The conversion coating system according to claim 1, wherein the second conversion coating composition further comprises copper in a concentration of up to about 50 ppm.

15. The conversion coating system according to any one of the foregoing claims, wherein the first conversion coating composition does not include a source of phosphorus.

16. A method for conversion coating of a multi-metal article comprising: (i) contacting a multi-metal article that comprises a first portion comprising steel, galvanized steel, alloy-galvanized steel, or any combination thereof, and a second portion comprising aluminum or aluminum alloy, with a first conversion coating composition comprising bismuth and organic acid, wherein the first conversion coating composition has an acidic pH, preferably in a range of about 2.0 to about 6.0, more preferably about 2.5 to 5.5 and a temperature of at least about 10°C during operation of the system and not more than 100°C, desirably about 10-70°C, preferably about 10-54°C, for a time sufficient to form on at least one surface of the first portion of the article a bismuth-containing conversion coating layer having a coating weight of about 50-5000 mg / m2; (ii) optionally, rinsing the multi-metal article with an aqueous rinse; and, (iii) contacting the multi-metal article with a second conversion coating composition comprising zirconium; fluoride; and, nitrate; wherein the second conversion coating composition has an acidic pH, desirably about 3.0 to 6.0, preferably about 3.5-5.0 and a temperature of at least about 10°C during operation of the system and not more than 100°C, desirably about 20-65°C, preferably about 20-54°C, for a time sufficient to form on at least one surface of the second portion of the multi-metal article a zirconium-containing conversion coating layer having a coating weight of about 10 to 200 mg / m2.

17. The method according to claim 16, wherein the bismuth is present in the first conversion coating composition in a concentration of about 25 to 5000 ppm, and the organic acid is present in the first conversion coating composition in a concentration of about 50-75,000 ppm.

18. The method according to claim 16, wherein second conversion coating composition comprises the zirconium in a concentration of about 50-500 ppm; free fluoride in a concentration of about 10-100 ppm; total fluoride in a concentration of about 150-2,000 ppm; and, the nitrate in a concentration of about 600-10,000 ppm.

19. The method according to claim 16, wherein the bismuth is present in the first conversion coating composition in a concentration of about 100 to 1000 ppm.

20. The method according to claim 16, wherein the organic acid is present in the first conversion coating composition in a concentration of about 500 to 5000 ppm.

21. The method according to claim 16, wherein the organic acid in the first conversion coating composition includes multiple carboxylic acid functionalities.

22. The method according to claim 16, wherein the organic acid in the first conversion coating composition comprises tartaric acid.

23. The method according to claim 16, wherein the first conversion coating composition further comprises free fluoride in a concentration up to about 5000 ppm.

24. The method according to claim 16,wherein the first conversion coating composition further comprises a complex fluoroacid in a concentration up to about 5000 ppm.

25. The method according to claim 16,wherein the first conversion coating composition further comprises copper (II) ions in a concentration up to about 200 ppm.

26. The method according to claim 16, wherein the first conversion coating composition does not include a source of phosphorus.

27. The method according to claim 16, wherein the zirconium is present in the second conversion coating composition in a concentration of about 100-200 ppm.

28. The method according to claim 16, wherein the zirconium in the second conversion coating composition is provided as hexafluorozirconic acid or hexafluorozirconate ions.

29. The method according to claim 16, wherein the second conversion coating composition further comprises copper in a concentration of up to about 50 ppm.

30. The method according to claim 16, wherein the second conversion coating composition further comprises silicon in a concentration of up to about 100 ppm.

31. The method according to claim 16, wherein the first conversion coating composition and the second conversion coating composition each individually contacts the multi-metal article by immersing the multi-metal article, by spraying, or any combination thereof, preferably in the absence of applied electromotive force.

32. The method according to claim 16, wherein the article is contacted with the first conversion coating composition for about 10 seconds to about 30 minutes.

33. The method according to claim 16, wherein the article is contacted with the second conversion coating composition for about 20 seconds to about 20 minutes.

34. The method according to claim 16, further comprising rinsing the article after contacting the article with the second conversion coating composition.

35. The method according to any one of claims 16-34, further comprising contacting the article with a sealer composition after contacting the article with the second conversion coating composition.

36. The method according to any one of claims 16-34, further comprising electrophoretically painting the article after contacting the article with the second conversion coating composition.

37. A multi-metal article comprising (i) a zinciferous or ferrous surface with an adherent first conversion coating layer comprising bismuth deposited on the zinciferous or ferrous surface, and (ii) an aluminum or aluminum alloy surface with a second conversion coating layer comprising ZrO2on the aluminum or aluminum alloy surface, wherein the first conversion coating layer and the second conversion coating layer were produced by a method according to any one of claims 16-34.

38. A multi-metal article comprising: a first portion comprising a zinciferous or ferrous surface and a first conversion coating layer on the zinciferous or ferrous surface, the first conversion coating layer comprising bismuth, a bismuth compound, or both in an amount of about 50 to 5000 mg / m2; and, a second portion comprising an aluminum or aluminum alloy surface and a second conversion coating layer on the aluminum or aluminum alloy surface, the second conversion coating layer comprising ZrO2.

39. The multi-metal article according to claim 38, wherein the bismuth or bismuth compound comprises elemental bismuth, bismuth oxide, bismuth hydroxides, or a combination thereof.

40. The multi-metal article according to claim 38, wherein the first conversion coating layer further comprises O, C, Cu, iron, zinc, or aluminum from at least the first portion of the multi- metal article, or any combination thereof.

41. The multi-metal article according to claim 38, wherein the first conversion coating layer comprises Zr in an amount of about 5 to 100 mg / m2.

42. The multi-metal article according to any one of claims 38-41, further comprising an electrophoretic paint coating on the first and second conversion coating layers.

43. The multi-metal article according to claim 42, wherein the electrophoretic paint coating on the first conversion coating layer has a thickness that is substantially the same as a thickness of the electrophoretic paint coating on the second conversion coating layer.

44. The multi-metal article according to claim 42, wherein no mapping defects are exhibited between the electrophoretic paint coating on the first conversion coating layer and the electrophoretic paint coating on the second conversion coating layer.

45. The multi-metal article according to claim 42, wherein the electrophoretic paint coating on the first conversion coating layer is substantially visually indistinguishable from the electrophoretic paint coating on the second conversion coating layer.

46. The multi-metal article according to claim 42, wherein the electrophoretic paint coating on both the first and second conversion coating layers has an adhesion characterized by at least 95% of the electrophoretic paint coating remaining following soaking of the article for 48 hours in water as measured according to GMW14829 / 14704.

47. The multi-metal article according to claim 42, wherein the first conversion coating layer and the second conversion coating layer each have a corrosion resistance characterized by a scribe creep of about 2.5 to 6 mm as measured according to GMW14872.