FORMATION OF CONVERSION COATING WITH ENHANCED ADHESION PROMOTION

Description

TECHNICAL FIELD

The present disclosure relates to conversion coatings and methods of manufacture thereof.

BACKGROUND

Chromate conversion coatings are widely used on aluminum alloys to improve corrosion resistance and paint adhesion. Replacement of traditional hexavalent chromium coatings with alternative materials has been underway due to health and environmental risks associated with Cr(VI). Non-hexavalent chromium conversion coatings, such as trivalent chromium conversion coatings, have been gained interest as an alternative coating type, however these alternative coating materials typically provide decreased adhesion properties for subsequent topcoats compared to hexavalent chromium conversion coatings.

Thus, a need remains for improved adhesive properties for non-hexavalent chromium conversion coatings.

SUMMARY

A conversion coating system includes a bifunctional polymeric additive composition and a conversion coating composition. The conversion coating composition includes a dye compound. The conversion coating composition and the bifunctional coating additive composition are configured to be provided separately, combined, or a combination thereof.

In one aspect, the conversion coating system may include less than 1 part per million (ppm) of hexavalent chromium.

In another aspect, the conversion coating composition may include a zirconium compound, a trivalent chromium compound, a titanium compound, a cerium compound, a lanthanum compound, a manganese compound, a silane compound, or a combination thereof.

In yet another aspect, the conversion coating system and the bifunctional polymeric additive composition may include a water-soluble polymer comprising a polymer backbone with a first functional group and a second functional group.

In yet another aspect, the first functional group may be a phosphonic acid group, a phosphoric acid group, or a combination thereof; and wherein the second functional group may be a carboxylic acid functional group.

In yet another aspect, the water-soluble polymer may be poly(vinyl phosphonic acid-co-acrylic acid) with a ratio of phosphonic acid functional groups to carboxylic acid functional groups of 90:10 to 10:90.

In yet another aspect, the ratio of the conversion coating composition to the bifunctional polymeric additive composition may be 90:10 to 99.9999:0.0001.

A bifunctional conversion coating including a bifunctional polymeric additive; a metal compound, a metalloid compound, or a combination thereof; and a dye. The metal compound comprises a trivalent chromium compound, a zirconium compound, a titanium compound, a cerium compound, a lanthanum compound, a manganese compound, or a combination thereof. The metalloid compound comprises a silane compound. The ratio of the bifunctional polymeric additive to the metal compound, the metalloid compound, or the combination thereof is 1:1 to 1:1000.

In one aspect, the bifunctional conversion coating may have a coating weight of 10 milligrams per square foot (mg/ft²) to 55 mg/ft².

A coated substrate includes the bifunctional conversion coating on a surface of the substrate.

In one aspect, the bifunctional conversion coating may have a color that is different than a color of the uncoated substrate, wherein the color of the bifunctional conversion coating may be macroscopically visible during irradiation with visible light, during irradiation with ultraviolet light, after irradiation with ultraviolet light, or a combination thereof.

In another aspect, the coated substrate may include a topcoat, wherein the bifunctional conversion coating and the topcoat include a layered coating. The layered coating may have a dry adhesion rating greater than 4B as measured in accordance with ASTM D3359 Method B.

In yet another aspect, the topcoat may be paint, a primer, an adhesive, a sealant, an erosion coating, an enamel, a lacquer, a varnish, an ink, or a combination thereof.

A method of manufacturing a coated substrate includes applying a conversion coating composition on a substrate to provide a conversion coating on a surface of the substrate; applying a bifunctional polymeric additive composition to the conversion coating on the surface of the substrate to convert the conversion coating a bifunctional conversion coating on the surface of the substrate; and rinsing the bifunctional conversion coating on the surface of the substrate with a rinse solution to provide a coated substrate.

In one aspect, the conversion coating composition and the bifunctional polymeric additive composition may be applied to the substrate simultaneously to provide the bifunctional conversion coating on the surface of the substrate.

In another aspect, the rinse solution may include the bifunctional polymeric additive composition or an additional portion of the bifunctional polymeric additive composition.

In yet another aspect, the applying of the bifunctional polymeric additive composition and the rinsing may be performed simultaneously.

In yet another aspect, the substrate may include aluminum, titanium, magnesium, cadmium, zinc, nickel, tin, silver, copper, iron, or a combination thereof.

In yet another aspect, the method may further include applying a topcoat solution to the coated substrate to provide a topcoat, wherein the bifunctional conversion coating is between the substrate and the topcoat.

In yet another aspect, the applying of the topcoat solution may be performed about one minute to about twelve months after rinsing the bifunctional conversion coating on the surface of the substrate.

BRIEF DESCRIPTION OF THE FIGURES

Referring now to the figures, which are exemplary embodiments, and wherein the like elements are numbered alike.

FIG. 1A is a cross-sectional view illustrating an embodiment of a product comprising a bifunctional conversion coating;

FIG. 1B is a cross-sectional view illustrating an embodiment of a product comprising a bifunctional conversion coating;

FIG. 1C is a cross-sectional view of area 110 of FIG. 1A; and

FIG. 2 is a flowchart of an embodiment of a method of applying a bifunctional conversion coating.

DETAILED DESCRIPTION

Disclosed herein is a conversion coating system. The system comprises a bifunctional polymeric additive composition and a conversion coating composition. Non-hexavalent chromium conversion coatings typically underperform analogous hexavalent chromium conversion coatings with regard to adhesion of a subsequent topcoat. Furthermore, non-hexavalent conversion coatings, such as traditional trivalent chromium conversion coatings, generally require a short window of time between the conversion coating process and subsequent application of a topcoat (e.g., paint, primer, adhesive, sealant, erosion coating, enamel, lacquer, varnish, ink, or the like) to maintain adequate adhesive properties (e.g., 24 hours or less). Substrates coated with the disclosed bifunctional conversion coating exhibit superior bonding and adhesion of a topcoat to the substrate in comparison to traditional trivalent chromium conversion coatings or the like. In addition, the color of the bifunctional conversion coating may be macroscopically visible during irradiation with visible light, during irradiation with ultraviolet light, after irradiation with ultraviolet light, or a combination thereof. Therefore, the disclosed coating facilitates manufacturing quality control with the macroscopic visibility and has a longer time allowance between conversion coating and subsequent application of a topcoat. A topcoat is often applied to a substrate to serve as an additional corrosion inhibiting surface. When a topcoat has poor adhesion, the underlying substrate may be exposed to corrosive conditions leading to material degradation, loss, and potentially failure of critical components.

The exemplary embodiments disclosed herein are illustrative of a bifunctional conversion coating with superior adhesion and manufacturing time flexibility. It should be understood, however, that the disclosed embodiments are merely examples of the present disclosure, which may be embodied in various forms. Therefore, details disclosed herein with reference to example coatings and associated processes of fabrication and use are not to be interpreted as limiting, but merely as the basis for teaching one skilled in the art how to make and use the bifunctional conversion coating of the present disclosure.

The conversion coating system includes a bifunctional polymeric additive composition with a conversion coating composition. The conversion coating system can be applied to a substrate to provide a bifunctional conversion coated substrate (also referred to as a “coated substrate” herein). The coated substrate may have a color that is different than a color of the uncoated substrate. The color of the coated substrate may be visually distinguished from the color of the uncoated substrate with the naked eye. For example, the color of the coating on the substrate may be macroscopically visible during irradiation with visible light, during irradiation with ultraviolet let, or a combination thereof. The coated substrate can further include a topcoat where the topcoat and the bifunctional conversion coating provide a layered coating on the substrate. The layered coating may provide a superior dry adhesion in comparison to the adhesion of a substrate coated with a trivalent chromium conversion coating and a topcoat.

FIGS. 1A and 1B illustrate cross-section views of embodiments of a bifunctional conversion coated substrate 100. As shown in FIG. 1A, a bifunctional conversion coating 104 may be disposed between a substrate 101 and a topcoat 105. The bifunctional conversion coating 104 may comprise a bifunctional polymeric additive 103, and a dyed conversion coating composition 102 including a metal compound, a metalloid compound, or a combination thereof and a dye compound. FIG. 1B illustrates an embodiment of a bifunctional conversion coated substrate 100 including a mixture of a bifunctional polymeric additive 103 and a polymeric additive 103b. FIG. 1C illustrates a cross-section view of area 110 of FIG. 1A. The bifunctional polymeric additive 103 can include a first functional group 107 and a second functional group 106 both attached to a polymer backbone 108. The polymeric additive 103a can comprise at least one functional group. The polymeric additive 103a can comprise the same or different functional groups as the bifunctional polymeric additive 103.

Conversion Coating System

A conversion coating system can include a bifunctional polymeric additive composition and a conversion coating composition. The bifunctional polymeric additive composition and the conversion coating composition can be combined into a single solution for ease of application. Alternatively, the bifunctional polymeric additive composition and the conversion coating composition can be used separately to apply a bifunctional conversion coating to a substrate. The ratio of the conversion coating composition to the bifunctional polymeric additive composition can be 80:20 to 20:80, 70:30 to 30:70, 90:10 to 99.9999:0.0001, or 50:50.

Conversion Coating Composition

The conversion coating composition may include a trivalent chromium conversion coating composition, a titanium/zirconium (Ti/Zr) conversion coating composition, a cerium (3+/4+) conversion coating composition, a lanthanum (3+/4+) conversion coating composition, a permanganate conversion coating composition, a silane conversion coating composition, a sol-gel conversion coating composition, or a combination thereof. The conversion coating composition used to prepare a conversion coating may include less than 1 part per million (ppm), or less than 1 part per billion (ppb) of hexavalent chromium. The conversion coating composition may include a zirconium compound, a trivalent chromium compound, a titanium compound, a cerium compound, a lanthanum compound, a manganese compound, a silane compound, or a combination thereof. Examples of the zirconium compound include alkali metal (e.g., potassium or sodium) hexafluorozirconate compounds, fluorozirconic acid, diammonium hexafluorozirconate, or a combination thereof. Examples of a trivalent chromium compound include ammonium chromium sulfate, chromium sulfate, chromium potassium sulfate, chromium hydroxide sulfate, chromium trifluoride, chromium trinitrate, or a combination thereof. Examples of the titanium compound include hexafluorotitanic acid, or the like.

The concentration of the metal compound, the metalloid compound, or the combination thereof in the conversion coating composition may be 0.01 weight percent (wt %) to 2 wt % based on a total weight of the conversion coating composition or 100 to 10,000 ppm of the conversion coating composition based on a total volume of the conversion coating composition.

The trivalent chromium compound may comprise water-soluble trivalent chromium compounds. The conversion coating composition solution may comprise one or more trivalent chromium compounds. For example, the conversion coating composition may comprise 1, 2, 3, or 4 trivalent chromium compounds. The trivalent chromium compound may comprise salts such as chromium sulfate, ammonium chromium sulfate, chromium potassium sulfate, chromium hydroxide sulfate, chromium trifluoride, chromium trinitrate, or a combination thereof.

The conversion coating composition may comprise one or more dye compounds. For example, the conversion coating composition may comprise 1, 2, 3, or 4 dye compounds. The dye compound may comprise strontium-containing compounds, manganese-containing compounds, rare earth metal-containing compounds, organic compounds, or other fluorescent or phosphorescent materials that upon irradiation with ultraviolet light emit light, typically in the human visible light spectrum. These fluorescent or phosphorescent materials can be either inorganic or organic molecules. The dye compound may comprise polycyclic or polyaromatic hydrocarbons containing heteroatoms such as sulfur, nitrogen, and oxygen. For example, appropriate materials that fluoresce in red include anthra-thioxanthene, thioxanthene benzanthrone, and xanthene, anthraquinones. Materials that fluoresce in yellow include benzothioxanthene-dicarboximide, aminoketones, naphthalimide, and perylene. Materials that fluoresce in blue include coumarin and hydroxycoumarin. Appropriate inorganic fluorescent materials include some divalent manganese containing salts such as manganese doped zinc silicate, which fluoresces green, or trivalent lanthanide salts. Useful phosphorescent materials include strontium aluminates, lanthanide doped (e.g., europium, dysprosium, cerium doped) or manganese doped strontium aluminates, or copper activated zinc sulfide. The dye compound may comprise a mordant dye compound. “Mordant dye compound” or “mordant dye”, as used herein, refers to a compound that forms insoluble colored complexes with a metal salt such as aluminum, chromium, or iron. Examples of mordant dye compounds include mordant red 11 (alizarin), mordant red 19, mordant blue 9, mordant blue 13, mordant blue 29, mordant blue 79, mordant brown 40, mordant orange 1, mordant orange 6, mordant yellow 5, mordant yellow 8, mordant yellow 30, tannic acid or the like. Examples of suitable dye compounds include an azo dye, an anthraquinone dye, a methine dye, a triphenylmethane dye, a mordant dye, or a combination thereof. The concentration of the dye compound in the conversion coating composition may be 0.01 wt % to 15 wt %, 0.05 wt % to 10 wt %, or 0.01 wt % to 2 wt % based on a total weight of the conversion coating composition.

The solvent of the conversion coating composition can be water, methanol, ethanol, isopropanol or a combination thereof.

The conversion coating composition may comprise a commercially available conversion coating composition or a combination thereof. Examples of suitable commercially available conversion coating compositions include CHEMEON TCC coatings (Chemeon eTCP, Chemeon eTCP RTU, Chemeon TCP-HF, or Chemeon TCP NP), SOCOMORE TCC coatings (Socomore TCS/PACS or Socomore TCS Colored RTU), SurTec TCC coatings (SurTec 650V, SurTec 650, or SurTec 650C), HENKEL non-hexavalent chromium conversion coatings (Bonderite M-CR 871 AERO, Bonderite M-CR T5900 RTU AERO, Bonderite M-NT 5200 AERO, Bonderite M-NT 5700 AERO, or Bonderite M-NT 65000), ELECTROBRITE Aluminum Chromate 190, ALUMINESCENT LQ, or IRIDITE NCP.

Bifunctional Polymeric Additive Composition

The bifunctional polymeric additive composition may comprise a bifunctional polymeric additive 103. The bifunctional polymeric additive 103 can be a water-soluble polymer with a first functional group 107 and a second functional group 106. Examples of suitable functional groups include an epoxide group, an alcohol group, a carbonyl group, an amine group, a thiol group, an isocyanate group, a nitrile group, an aromatic hydrocarbon group, a heteroaromatic group, an alkene group, an alkyne group, an aldehyde group, a ketone group, a siloxane group, a silane group, a phosphoric acid group, a phosphonic acid group, or a carboxylic acid group. For example, the first functional group may be a phosphonic acid functional group, a phosphoric acid functional group, or a combination thereof and the second functional group may be a carboxylic acid functional group. “Aromatic hydrocarbon group”, as used herein, refers to a substituted or unsubstituted C₆ to C₂₀ aryl group. Examples of a C₆ to C₂₀ aryl group include a phenyl group, a naphthyl group, an anthracenyl group, or the like. “Heteroaromatic group”, as used herein, refers to a substituted or unsubstituted C₁ to C₂₀ heteroaryl group including heteroatoms such as O, N, P, S, or the like. Examples of a C₁ to C₂₀ heteroaryl group include a pyridyl group, a pyrrolyl group, a furanyl group, a thienyl group, an indolyl group, or the like.

The bifunctional polymeric additive may comprise a polymer backbone 108 substituted with both the first functional group and the second functional group. For example, the bifunctional polymeric additive may be copolymers prepared from at least one first functional group monomer and at least one second functional group monomer. The copolymers can be double or triple copolymers. Examples of the first functional group monomers include vinyl phosphonic acid, vinyl phosphate, or the like. Examples of the second functional group monomers include acrylic acid, methacrylic acid, or the like. The ratio of the first functional group monomer to the second functional group monomer in the final copolymer may be 90:10, to 10:90, 80:20 to 20:80, 82.5:17.5, or 30:70. The molecular weight of the bifunctional polymeric additive may be 5,000 grams per mole (g/mol) to 300,000 g/mol. Examples of a bifunctional polymeric additive include poly(vinyl phosphonic acid-co-acrylic acid), poly(vinyl phosphonic acid-co-methacrylic acid), poly(vinyl phosphate-co-acrylic acid), poly(vinyl phosphate-co-methacrylic acid), or a combination thereof. The ratio of the phosphonic acid functional groups to the carboxylic acid functional groups in the bifunctional polymeric additive can be 90:10, to 10:90, 80:20 to 20:80, 82.5:17.5, or 30:70. The concentration of the bifunctional polymeric additive in the bifunctional polymeric additive composition may be 0.01 wt % to 2 wt % based on a total weight of the polymeric additive composition, or 10 ppm to 1,000 μm, or 50 ppm to 500 ppm based on a total volume of the bifunctional polymeric additive composition.

The bifunctional polymeric additive composition may further comprise a polymeric additive 103a. The polymeric additive 103a can comprise at least one functional group. The polymeric additive 103a can comprise the same or different functional groups as the bifunctional polymeric additive 103. Examples of the functional groups substituted on the polymeric additive 103a include epoxides, alcohols, carbonyls, amines, thiols, isocyanates, nitriles, aromatic hydrocarbons, heteroaromatics, alkenes, alkynes, aldehydes, ketones, siloxanes, silanes, phosphonic acids, phosphoric acids, carboxylic acids, or the like. Examples of the polymeric additive 103a include poly(vinyl phosphonic acid), poly(vinyl phosphate), poly(acrylic acid), poly(methacrylic acid), or the like. The ratio of the bifunctional polymeric additive 103 to the polymeric additive 103a in the bifunctional polymeric additive composition can be 99:1 to 1:99, 90:10 to 10:90, 70:30 to 30:70, or 50:50.

The bifunctional polymeric additive composition may further comprise additives such as a monomer of a functional group. Examples of the monomer of a functional group include vinyl phosphate, vinyl phosphonic acid, acrylic acid, methacrylic acid, or the like. The concentration of the monomer of a functional group in the bifunctional polymeric additive solution may be 0.001 wt % to 2 wt %, or 0.005 wt % to 1 wt % based on the total weight of the bifunctional polymeric additive composition.

The solvent of the bifunctional polymeric additive composition can be water, methanol, ethanol, isopropanol, butyl alcohol, sec-butyl alcohol, isobutyl alcohol, tert-butyl alcohol, pentanol, cyclohexyl alcohol, phenol, or a combination thereof.

Method of Applying a Bifunctional Conversion Coating

FIG. 2 illustrates a flow diagram of a method of applying a bifunctional conversion coating to a substrate to manufacture a coated substrate. The substrate may include aluminum, titanium, magnesium, cadmium, zinc, nickel, tin, silver, copper, iron, or a combination thereof. As shown in FIG. 2, the method can include pre-cleaning the substrate for coating with steps 201 to 204, these pre-cleaning steps can include cleaning the substrate with an organic solvent or an alkali cleaner to provide a cleaned substrate (step 201), rinsing the cleaned substrate to provide a cleaned, rinsed substrate (step 202), deoxidizing the cleaned, rinsed substrate to provide a deoxidized substrate (step 203), and rinsing the deoxidized substrate to provide a rinsed, deoxidized substrate that is ready for coating (step 204). The method can include applying a conversion coating composition to the rinsed, deoxidized substrate to provide a conversion coating on a surface of the substrate (step 205a) and applying a bifunctional polymeric additive composition to the conversion coating on the surface of the substrate to provide a bifunctional conversion coating on the surface of the substrate (step 205b). In an embodiment, the conversion coating composition and the bifunctional polymeric additive composition can be applied simultaneously as two separate solutions or the two solutions can be pre-mixed and applied simultaneously as a single solution to the substrate (i.e., the rinsed, deoxidized substrate) as combined step 205a/205b. In another embodiment, the conversion coating composition and the bifunctional polymeric additive composition can be applied consecutively.

After application of the conversion coating composition and the bifunctional polymeric additive composition, the bifunctional conversion coating on the surface of the substrate may be rinsed with a rinse solution to provide a coated substrate (step 206). The coated substrate can be dried at step 207. In an embodiment, the rinse solution may further comprise the bifunctional polymeric additive composition or an additional portion of the bifunctional polymeric additive composition. For example, the applying of the bifunctional polymeric additive composition and the rinsing steps (step 205b and step 206) may be performed simultaneously. In another embodiment, the applying of the bifunctional polymeric additive composition may be followed by a rinsing step, wherein the rinse solution comprises an additional portion of the bifunctional polymeric additive composition. A concentration of the bifunctional polymeric additive composition in step 205b may be the same or different as a concentration of the bifunctional polymeric additive composition in the rinse solution of step 206. A ratio of a total volume of the rinse solution to a total volume of the polymeric additive composition may be 10:1 to 1:10, 2:1 to 1:2, or 1:1. The concentration of the bifunctional polymeric additive composition in the rinse solution may be 0.01 wt % to 2 wt %, 0.01 wt % to 100 wt %, 0.1 wt % to 100 wt %, 1 wt % to 100 wt %, 10 wt % to 80 wt %, 20 wt % to 60 wt %, or 50 wt % based on a total weight of the rinse solution. The concentration of the bifunctional polymeric additive in the rinse solution may be 10 ppm to 1,000 ppm or 50 ppm to 500 ppm based on a total volume of the rinse solution.

The cleaning of the substrate in step 201, can comprise treating the substrate with an alkali cleaner, an organic solvent, or a combination thereof. The rinse solution used for rinsing of the cleaned substrate (step 202) and the rinsing of the deoxidized substrate (step 204) can independently comprise a solvent of water, methanol, ethanol, isopropanol, or a combination thereof.

In an embodiment, the rinse solution of step 206 can comprise the bifunctional polymeric additive composition or can comprise an additional portion of the bifunctional polymeric additive composition. The additional portion of the bifunctional polymeric additive composition may comprise the same components of the bifunctional polymeric additive composition used in step 205b or the additional portion of the bifunctional polymeric additive composition may comprise different components and/or different component ratios than the bifunctional polymeric additive composition used in step 205b. The additional portion of the bifunctional polymeric additive composition may include a bifunctional polymeric additive 103, a bifunctional polymeric additive 103 and a monomer of a functional group, a bifunctional polymeric additive 103 and a polymeric additive 103a, or a bifunctional polymeric additive 103, a polymeric additive 103a, and a monomer of a functional group.

For example, the applying of the bifunctional polymer composition in step 205b may comprise a solution of a bifunctional polymeric additive and a monomer of a functional group in a molar ratio of 50:50 and the rinse solution of step 206 may also comprise the solution of a bifunctional polymeric additive and a monomer of a functional group in a molar ratio of 50:50. In another embodiment, the applying of the bifunctional polymeric additive composition in step 205b may comprise a solution of a bifunctional polymeric additive and a monomer of a functional group in a molar ratio of 50:50 and the rinse solution of step 206 may also comprise the solution of a bifunctional polymeric additive and a monomer of a functional group in a molar ratio of 1:9.

Drying of the rinsed, coated substrate at step 207 to provide the dried substrate can include air drying at room temperature (e.g., about 25° C.), or drying under application of additional heat to remove the solvent and other volatile compounds. Drying can be performed for 30 seconds to 24 hours, 1 hour to 12 hours, or until application of a topcoat.

The method can further comprise applying a topcoat solution to the dried substrate to provide a topcoat. The bifunctional conversion coating can be between the substrate and the topcoat. Applying a topcoat solution to the dried substrate may be performed about one minute to 12 months, or one day to one week, after drying of the bifunctional conversion coating on the surface of the substrate. The disclosed bifunctional conversion coating on the surface of the substrate accommodates extending manufacturing times to provide flexibility and shipping for application of a final topcoat to the bifunctional conversion coating. The applying of the conversion coating composition and/or the applying of the bifunctional polymeric additive composition may be performed with immersion of at least a portion of the substrate, with a pen, with a brush, with a spray, with a wipe, or with a combination thereof.

Bifunctional Conversion Coating

The bifunctional conversion coating on the substrate can include a bifunctional polymeric additive; a metal compound, a metalloid compound, or a combination thereof; and a dye compound. The metal compound may comprise a trivalent chromium compound, a zirconium compound, a titanium compound, a cerium compound, a lanthanum compound, a manganese compound, or a combination thereof. The metalloid compound may comprise a silane compound. The bifunctional conversion coating may have a coating weight of 10 mg/ft² to 55 mg/ft² as measured by MIL-DTL-81706 paragraph 4.5.4, or the like. The ratio of the bifunctional polymeric additive to the metal compound, the metalloid compound, or the combination thereof may be 1:1 to 1:1000, 1:9 to 1:100, or 1:20 to 1:50. The concentration of dye in the conversion coating may be 0.01 wt % to 15 wt % or 0.1 wt % to 10 wt % based on a total weight of the bifunctional conversion coating.

The bifunctional conversion coating can be on a surface of the substrate to provide a coated substrate. The bifunctional conversion coating can provide a color to the coated substrate that is different than a color of the uncoated substrate. The color of the bifunctional conversion coating can be macroscopically visible during irradiation with visible light, during irradiation with ultraviolet light, after irradiation with ultraviolet light (e.g., fluorescence or phosphorescence), or a combination thereof to improve quality control assessments of coating coverage. Due to the presence of a visible coating, voids and imperfections in the bifunctional conversion coating can be identified by the naked eye to accommodate corrective applications of the bifunctional conversion coating system to the substrate.

The coated substrate can further comprise a topcoat. The bifunctional conversion coating and the topcoat together can comprise a layered coating with superior adhesion. The layered coating may have adhesion greater than a conventional non-hexavalent chromium conversion coating. Robust adhesive bonding of a topcoat to an underlying substrate with an interposed conversion coating can provide significant safety protection. Highly engineered products typically depend on the structural integrity of the entire component. If bonded coating layers on a component provide insufficient adhesion, the component may cease to function or even become liberated within a system, such as an engine. Depending on the function or location of the component, loss of adhesion may lead to catastrophic system failure.

The disclosed layered coating may have a adhesion rating of 3A or greater, 4A or greater, or a rating of 5A, as measured in accordance with ASTM D3359 Method A. The disclosed layered coating may have a dry adhesion rating of 3B or greater, 4B or greater, or a rating of 5B, as measured in accordance with ASTM D3359 Method B. The layered coating may have adhesion that meets the criteria of FED-STD-141, Method 6301.3 with no intercoat separation between the topcoat, the bifunctional conversion coating, and the substrate. The layered coating may have an adhesion rating of 1 or 0, as measured in accordance with ISO 2409. The topcoat may be a paint, a primer, an adhesive, a sealant, an erosion coating, an enamel, a lacquer, a varnish, an ink, or a combination thereof. The coating weight of the topcoat may be 10 mg/ft² to 55 mg/ft² as measured by MIL-DTL-81706 paragraph 4.5.4, or the like. An “erosion coating”, as used herein, refers to material applied to protect an underlaying coating or substrate from damage due to particulate impingement (e.g., a polyurethane material, a silicone material, or a fluoroelastomer material).

It is noted that the bifunctional conversion coatings prepared with the disclosed conversion coating systems can provide superior adhesion properties in comparison to traditional trivalent chromium conversion coatings. Furthermore, the methods of the present disclosure provide improved manufacturing flexibility with maintenance of adhesive properties with prolonged delays (e.g., 1 month) between application of the bifunctional conversion coating and the topcoat.

While particular embodiments have been described, alternatives, modifications, variations, improvements, and substantial equivalents that are or may be presently unforeseen may arise to applicants or others skilled in the art. Accordingly, the appended claims as filed and as they may be amended are intended to embrace all such alternatives, modifications variations, improvements, and substantial equivalents.

The ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other (e.g., ranges of “up to 25 wt. %, or, more specifically, 5 wt. % to 20 wt. %”, is inclusive of the endpoints and all intermediate values of the ranges of “5 wt. % to 25 wt. %,” and so forth). “Combinations” is inclusive of blends, mixtures, alloys, reaction products, and the like. The terms “first,” “second,” and the like, do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The terms “a” and “an” and “the” do not denote a limitation of quantity and are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. “Or” means “and/or” unless clearly stated otherwise. Reference throughout the specification to “some embodiments”, “an embodiment”, and so forth, means that a particular element described in connection with the embodiment is included in at least one embodiment described herein, and may or may not be present in other embodiments. In addition, it is to be understood that the described elements may be combined in any suitable manner in the various embodiments. A “combination thereof” is open and includes any combination comprising at least one of the listed components or properties optionally together with a like or equivalent component or property not listed.

Unless defined otherwise, technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in the art to which this application belongs. All cited patents, patent applications, and other references are incorporated herein by reference in their entirety. However, if a term in the present application contradicts or conflicts with a term in the incorporated reference, the term from the present application takes precedence over the conflicting term from the incorporated reference.

Although the conversion coating systems, coatings, and methods of the present disclosure have been described with reference to example embodiments thereof, the present disclosure is not limited to such example embodiments and/or implementations. Rather, the conversion coating systems, coatings, and methods of the present disclosure are susceptible to many implementations and applications, as will be readily apparent to persons skilled in the art from the disclosure hereof. The present disclosure expressly encompasses such modifications, enhancements and/or variations of the disclosed embodiments. Since many changes could be made in the above construction and many widely different embodiments of this disclosure could be made without departing from the scope thereof, it is intended that all matter contained in the drawings and specification shall be interpreted as illustrative and not in a limiting sense. Additional modifications, changes, and substitutions are intended in the foregoing disclosure. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the disclosure.