Coating compositions having Anti-corrosion properties

Abstract

The disclosure relates to corrosion-inhibiting coating compositions, coated articles and methods for inhibiting corrosion on substrates. The compositions disclosed herein include a polymeric binder resin system and a corrosion inhibiting solar reflective compound having a specific total solar reflectance (TSR) and a specific HOMO-LUMO bandgap.

Description

Attorney Docket No. 104876-1001COATING COMPOSITIONS HAVING ANTI-CORROSION PROPERTIESCROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority from U. S. Provisional Application 63 / 759,873, filed on February 18, 2025, the entire content of which is hereby incorporated by reference into this application.FIELD OF INVENTION

[0002] The present invention relates to coating compositions incorporating corrosion-inhibiting compounds for use in coating metal substrates susceptible to corrosion.BACKGROUND[0003 J The inclusion of strontium chromate (hexavalent chromium) in coating formulations is known to be one of the most effective means for corrosion inhibition on metallic substrates, such as aluminum, steel or galvanized steel exposed to corrosive environments. Although more environmentally friendly alternatives are commercially available, none have demonstrated equivalent corrosion inhibiting properties, and most are market specific.

[0004] Other known corrosion inhibiting additives include phosphates, benzotriazoles, and acid-functionalized inhibitors. However, each of these types of inhibitors have their own drawbacks. For example, phosphates do not provide the same degree of inhibition, and acidic inhibitors function only in specific markets, and have not demonstrated substantial long-term inhibition.Attorney Docket No. 104876-1001

[0005] There remains a need for compounds, which are highly effective at corrosion inhibition while being hexavalent chromium free, to eliminate the human and environment hazards associated with coatings incorporating strontium chromate.SUMMARY[0006| The present invention relates to coating compositions incorporating compounds which have been discovered to have corrosion-inhibiting properties. Coated articles incorporating anti-corrosion coatings are also disclosed. The coating formulations disclosed herein have the advantage of exhibiting a high degree of corrosion inhibition on metallic substrates, while being more environmentally friendly than leading chromium or chromate inhibitors.

[0007] In certain embodiments, the coating composition disclosed herein includes a polymeric resin binder system and at least one corrosion-inhibiting compound. The corrosion-inhibiting compound is a solar reflective compound having a total solar reflectance 'TSR”) of about 40% or higher and a HOMO-LUMO band gap of about 2.2-4.0 eV. The HOMO-LUMO bandgap is the energy difference between a molecule’s highest occupied molecular orbital (HOMO) and its lowest unoccupied molecular orbital (LUMO), and is generally the lowest energy electronic excitation that is possible in a molecule. A smaller HOMO-LUMO gap typically corresponds to higher stability of a material.[0008| It has been discovered that the use of solar reflective pigments in primer coating formulations, can effectively inhibit corrosion activity, particularly in metallic substrates. The inventors have discovered that solar reflective pigments having a TSR of 40% or more and HOMO-LUMO bandgap between 2.2 - 4.0 eV have shown excellent and potentially improved corrosion inhibition properties, when compared to the standardAttorney Docket No. 104876-1001chromate inhibitors, which are typically used in industry. Suitable solar reflective pigments for use in the coating compositions disclosed herein, which satisfy' the TSR and HOMO-LUMO parameter, include bismuth copper oxide (Bi2CuO4), bismuth oxide (BiO3), bismuth oxyhalide, bismuth vanadate (BiVO4), and cobalt titanate (Co2TiO6), cobalt aluminate, cobalt chromite, chromium green-black hematite, zinc titanate, niobium sulfur tin zinc oxide, and ferric ammonium ferrocyanide.[0009} It is appreciated that certain features of the invention, which are, for clarity', described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination. All combinations of the embodiments pertaining to the invention are specifically embraced by the present invention and are disclosed herein just as if each and every combination was individually and explicitly disclosed. In addition, all subcombinations of the various embodiments and elements thereof are also specifically embraced by the present invention and are disclosed herein just as if each and every such subcombination was individually and explicitly disclosed herein. Coated articles and methods for corrosion-inhibition on metallic substrates are also disclosed herein.Selected Definitions and Nomenclature{0010 J As used herein, the term “HOMO-LUMO bandgap’' refers to the energy difference between amolecule's highest occupied molecular orbital (HOMO) and its lowest unoccupied molecular orbital (LUMO), and is generally the lowest energy electronic excitation that is possible in a molecule. It is measured in units of electronvolts (eV).Attorney Docket No. 104876-100110011] As used herein, then term “total solar reflectance” or “TSR” refers to the capability of a solar reflective pigment or a coating containing said pigment to reflect solar radiation and it is expressed as a percentage between 0-100%. The higher the percentage value, the more effective a pigment compound or coating will be at reflecting solar radiation.[00121 Unless otherwise indicated, the term “polymer” includes both homopolymers and copolymers (i.e., polymers of two or more different monomers). Similarly, unless otherwise indicated, the use of a term designating a polymer class such as, for example, “polyester” is intended to include both homopolymers and copolymers (e.g., polyester-imide copolymers).

[0013] The term “crosslinker” refers to a molecule capable of forming a covalent linkage between polymers or between two different regions of the same polymer.

[0014] The term “self-crosslinking,” when used in the context of a self-crosslinking polymer, refers to the capacity of a polymer to enter into a crosslinking reaction with itself and / or another molecule of the polymer, in the absence of an external crosslinker, to form a covalent linkage therebetween. Typically, this crosslinking reaction occurs through reaction of complimentary reactive functional groups present on the self-crosslinking polymer itself or two separate molecules of the self-crosslinking polymer.

[0015] The term “thermoplastic” refers to a material that melts and changes shape when sufficiently heated and hardens when sufficiently cooled. Such materials are typically capable of undergoing repeated melting and hardening without exhibiting appreciableAttorney Docket No. 104876-1001chemical change. In contrast, a “thermoset” refers to a material that is crosslinked and does not “melt.”[0016 J The term “substantially free” of a particular component means that the compositions of the present invention contain less than 5 wt % of the component, based on the total weight of the composition.

[0017] The term “essentially free” of a particular component means that the compositions of the present invention contain less than 1 wt % of the component, based on the total weight of the composition.[0018| The term “on,” when used in the context of a coating applied on a surface or substrate, includes both coatings applied directly or indirectly to the surface or substrate. Thus, for example, a coating applied to a primer layer overlying a substrate constitutes a coating applied on the substrate.

[0019] The singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0020] The term "and / or" or “and or” refers to and encompasses any and all possible combinations of one or more of the associated listed items.

[0021] The term "about," when referring to a measurable value such as length, width, diameter, radius, or an amount of a compound, dose, time, temperature, and the like, is meant to encompass variations of 10%, 5%, 1%, 0.5%, or even 0.1% of the specified amount.Attorney Docket No. 104876-1001J0022] In the interest of brevity and conciseness, any ranges of values set forth in this specification contemplate all values within the range and are to be construed as support for claims reciting any sub-ranges having endpoints which are real number values within the specified range in question. By way of a hypothetical illustrative example, a disclosure in this specification of a range of from 1 to 5 shall be considered to support claims to any of the following ranges: 1-5; 1-4; 1-3; 1-2; 2-5; 2-4; 2-3; 3-5; 3-4; and 4-5.J0023] The term “substantially” is utilized herein to represent the inherent degree of uncertainty that can be attributed to any quantitative comparison, value, measurement, or other representation. The term “substantially” is also utilized herein to represent the degree by which a quantitative representation can vary from a stated reference without resulting in a change in the basic function of the subj ect matter at issue.|0024| The terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. Unless otherwise defined, all terms, including technical and scientific terms used in the description, have the same meaning as commonly understood by one of ordinary' skill in the art to which this disclosure belongs. In the event of conflicting terminology, the present specification is controlling.[0025| The terms “preferred” and “preferably” refer to embodiments that may afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one orAttorney Docket No. 104876-1001more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the present disclosure(0026] As used throughout this description, and in the claims, a list of items joined by the term "at least one of or ‘‘one or more of’ can mean any combination of the listed terms. For example, the phrase “at least one of X, Y or Z'’ can mean X; Y; Z; X and Y; X and Z; Y and Z; or X, Y and Z.

[0027] All patents, patent applications and publications referred to herein are incorporated by reference in their entirety.BRIEF DESCRIPTION OF FIGURES

[0028] FIG. 1 illustrates corrosion test results on cold rolled steel substrate (60 cycles, SAE J2334 test method): positive control (left), negative control (middle), coated sample of interest with zinc titanate as the corrosion inhibitor (right).10029] FIG. 2 illustrates corrosion test results on cold rolled steel substrate (80 cycles, SAE J2334 test method): positive control (first panel), negative control (second panel), coated sample of interest with cobalt titanate (third panel), bismuth vanadate (fourth panel), and bismuth oxide (fifth panel) as the corrosion inhibitor (right).Attorney Docket No. 104876-1001(0030) FIG. 3 illustrates corrosion test results on aluminum 2024-T3 substrates (80 cycles, SAE J2334 test method): positive control (first panel), negative control (second panel), coated sample of interest wi th cobalt titanate (third panel), bismuth vanadate (fourth panel), and bismuth oxide (fifth panel) as the corrosion inhibitor (right).(0031} FIG. 4 illustrates a graphical result of cyclic potentioadynamic polarization (CPDP) curve for a control system of strontium chromate in 5% NaCl solution for an uncoated aluminum 2024-T3 substrate.[0032| FIG.5 illustrates a graphical result of cyclic potentioadynamic polarization (CPDP) curve for a control system of Yellow 10P150 solar reflecting pigment displaying similar behavior in 5% NaCl solution (as compared to strontium chromate) for an uncoated aluminum 2024-T3 substrate.[003 1 FIG. 6 illustrates a graphical result of cyclic potentioadynamic polarization (CPDP) curve for a control system of zin titanate solar reflecting pigment, displaying similar behavior in 5% NaCl solution (as compared to strontium chromate) for an uncoated aluminum 2024-T3 substrate.[0034| FIG.7 illustrates a graphical result of cyclic potentioadynamic polarization (CPDP) curve for a control system of Eclipse Green solar reflecting pigment, displaying similar behavior in 5% NaCl solution (as compared to strontium chromate) for an uncoated aluminum 2024-T3 substrate.[00351 FIG. 8 illustrates a graphical result of cyclic potentioadynamic polarization (CPDP) curve for a control system of Camo Green solar reflecting pigment, displayingAttorney Docket No. 104876-1001similar behavior in 5% NaCl solution (as compared to strontium chromate) for an uncoated aluminum 2024-T3 substrate.

[0036] FIG. 9 illustrates a graphical result of cyclic potentioadynamic polarization (CPDP) curve for a control system of Lysopac Orange solar reflecting pigment, displaying similar behavior in 5% NaCl solution (as compared to strontium chromate) for an uncoated aluminum 2024-T3 substrate.

[0037] FIG.10 illustrates a graphical result of cyclic potentioadynamic polarization (CPDP) curve for a control system of Blue Cobalt Aluminate solar reflecting pigment, displaying similar behavior in 5% NaCl solution (as compared to strontium chromate) for an uncoated aluminum 2024-T3 substrate.

[0038] FIG. 11 illustrates a graphical result of cyclic potentioadynamic polarization (CPDP) curve for a control system of bismuth vanadate solar reflecting pigment, displaying similar behavior in 5% NaCl solution (as compared to strontium chromate) for an uncoated aluminum 2024-T3 substrate.

[0039] FIG. 12 illustrates a graphical result of cyclic potentioadynamic polarization (CPDP) curve for a control system of cobalt titanate solar reflecting pigment, displaying similar behavior in 5% NaCl solution (as compared to strontium chromate) for an uncoated aluminum 2024-T3 substrate.

[0040] FIG. 13 illustrates a graphical result of cyclic potentioadynamic polarization (CPDP) curve for a control system of yttrium indium manganese blue solar reflecting pigment, displaying similar behavior in 5% NaCl solution (as compared to strontium chromate) for an uncoated aluminum 2024-T3 substrate.Attorney Docket No. 104876-1001(0041) FIG. 14 illustrates a graphical result of cyclic potentioadynamic polarization (CPDP) curve for a control system of bismuth manganese oxide / bismuth oxide black solar reflecting pigment, displaying similar behavior in 5% NaCl solution (as compared to strontium chromate) for an uncoated aluminum 2024-T3 substrate (0042] FIG. 15 illustrates a graphical result of cyclic potentioadynamic polarization (CPDP) curve for a control system of manganese ferrite black spinel solar reflecting pigment, displaying similar behavior in 5% NaCl solution (as compared to strontium chromate) for an uncoated aluminum 2024-T3 substrate(0043] FIG. 16 shows images of samples illustrating inhibition by CPDP in 5% NaCl solution for an uncoated aluminum 2024-T3 substrate.(0044] FIG. 17 is a box plot of corrosion potential (Ecorr) of the SR pigment inhibitors disclosed herein.

[0045] FIG. 18 is a box plot of the Delta E of the SR pigment inhibitors disclosed herein.DETAILED DESCRIPTION

[0046] Disclosed herein are corrosion-resistant coating compositions, coated articles, and methods for improving the corrosion resistance of coated articles.

[0047] In certain embodiments, the coating compositions disclosed have the advantage of being substantially free of hexa-valent chromium containing compounds, while exhibiting high degree of corrosion inhibition on metallic substrates. Thus, this disclosure details a new class of compounds for use in corrosion inhibition in coatingAttorney Docket No. 104876-1001formulations, which are environmentally safe and highly effective, providing an advantageous alternative to chromium or chromate inhibitors.

[0048] In one embodiment, the coating composition disclosed herein includes a polymeric resin binder system and at least one corrosion-inhibiting compound. The corrosion-inhibiting compound is a solar reflective compound having a total solar reflectance (“TSR”) of about 40% or higher and a HOMO-LUMO band gap of about 2.2-4.0 eV. The HOMO-LUMO bandgap is the energy difference between a molecule’s highest occupied molecular orbital (HOMO) and its lowest unoccupied molecular orbital (LUMO), and is generally the lowest energy electronic excitation that is possible in a molecule. A smaller HOMO-LUMO gap typically corresponds to higher stability of a material.

[0049] The HOMO-LUMO bandgap should be higher than 4.13 eV to eliminate solar absorption. However, as the band gap increases, the refractive index decreases which weakens scattering and reflection. Therefore, for the purposes of this work, a band gap slightly lower than 4.13 eV is preferred. It is believed that LUMO is directly related to reduction potential which indicates ability to spontaneously be reduced.[00501 In one embodiment, the corrosion-inhibiting compound has a HOMO-LUMO band of about 2.2 to 4.0 eV, or any range or value therebetween. It has been discovered that the use of solar reflective pigments in primer coating formulations, can effectively inhibit corrosion activity, particularly in metallic substrates. The inventors have discovered that solar reflective pigments having a TSR of 40% or more and HOMO-LUMO bandgap between 2.2-4.0 eV have shown excellent and potentially improved corrosion inhibition properties, when compared to the standard chromate inhibitors, which are typically used in industry'. Suitable solar reflective pigments for use in the coatingAttorney Docket No. 104876-1001compositions disclosed herein, which satisfy the TSR and HOMO-LUMO parameter, include bismuth copper oxide (Bi2CuO4), bismuth oxide (BiO3), bismuth manganese oxide, bismuth oxyhalide, bismuth vanadate (BiVO4) manganese iron oxide, yttrium indium manganese oxide, and cobalt titanate (Co2TiO6), cobalt aluminate, cobalt chromite, chromium green-black hematite, zinc titanate, niobium sulfur tin zinc oxide, and ferric ammonium ferrocyanide. Table 1 lists several of the SR pigments mentioned herein, although this is not a list which is intended to be limiting, but simply exemplary.TABLE 1.SR Pigment Chemistry Cas #Cobalt Aluminate Cobalt Aluminate 1345-16-0Green Spinel V- 11633 Cobalt Titanate 68186-85-6Durovan 5000 PY184 Bismuth Vanadate 14059-33-7Strontium Chromate Strontium Chromate 7789-06-2Lysopac Orange 6280B Bismuth Oxyhalide; BiOBr(l- proprietary PO85 x)IxCamo Green PG26 Cobalt Chromite 68187-49-5Eclipse IR Green V- 12650 Chromium Green-Black Hematite 68909-79-5Zinc Titanate Zinc Titanate 12036-43-0Attorney Docket No. 104876-1001Bismuth OxideBismuth Oxide 1304-76-3 NanopowderYellow 1 OP 150 Niobium Sulfur Tin Zinc Oxide 1374645-21-2DCL-521 Milori Blue, PB Ferric Ammonium Ferrocyanide25869-00-5 27 (C6H4Fe2N7)Bismuth Copper Oxide Bismuth Copper Oxide 39368-32-612232-96-1 / 1304- Bismuth Oxide Black Bismuth Manganese Oxide76-3Manganese Ferrite BlackManganese Iron Oxide 68186-94-7 SpinelYttrium Indium Manganese Yttrium Indium Manganese1239902-45-4 Blue OxideIron Manganese Black Iron Manganese Oxide 12063-10-4Manganese Antimony Manganese oxide. Antimony68412-38-4 Titanium Buff Rutile oxide, Titanium oxideChrome Antimony Chromium oxide, Antimony68186-90-3 Titanium Buff Rutile oxide, Titanium oxideChrome Iron Nickel BlackChrome Iron Nickel Oxide 71631-15-7 SpinelAttorney Docket No. 104876-1001Chrome Tungsten Titanium Chromium oxide, Tungsten68186-92-5 Buff Rutile oxide, Titanium oxide[00511 In certain embodiments, the corrosion-inhibiting compound is present in an amount of about 0.5 - 20 wt. % based on the total weight of the coating composition, or 0.5-15 wt.%. or 0.5-10 wt.%, or 1.0 - 9.0 wt. %, or 2.0 - 8.0 wt % or 3.0 - 7.0 wt. %, or 4.0 - 6.0 wt. %, or preferably about 5.0 wt. %.[0052 J In embodiments, a combination of corrosion-inhibiting compounds can be incorporated in the coating composition. In further embodiments, the coating compositions comprise the SR pigment compounds detailed herein in addition to chromium or chromate based corrosion inhibitors. In some embodiments, the coating compositions include the SR pigment compounds detailed herein in combination with non-chromium or non-chromate based corrosion inhibitors known in the art, including phosphates, metal oxides, and the like, for example. In other embodiments, the coating compositions are essentially or substantially chromium or chromate free.

[0053] The corrosion inhibiting compounds described herein are incorporated in a polymer resin binder system. The polymer resin binder system includes a polymer resin and optionally a crosslinking agent. Polymer resins in the binder system may be thermosetting and / or thermoplastic. In certain embodiments, a thermoplastic resin useful in the practice of the present invention may be amorphous, crystalline or semicrystalline. Example polymer resins used in the binder system include acyclic, cyclic, branched, linear, aliphatic, or aromatic resins. In an aspect, the binder system described herein may beAttorney Docket No. 104876-1001waterborne, water-reducible, water-dispersible, or solvent-borne. Suitable polymeric resins include, without limitation, epoxy resin, acrylics, polyolefins, polyurethanes, polyamines, alkyds, polyesters, chlorinated resins, fluorinated resins, and the like. The choice of resin for a coating composition will be determined by the performance requirements of a given end use. In an aspect, the polymeric resin is a urethane, preferably a reaction product of one or more polyols with one or more acids or diols.[0054} Suitable polyols include, without limitation, including, for example, poly ether polyols, polyester polyols, and the like. For example, the polyol described herein may be a reaction product of an epoxide or epoxy-functional compound with an acid or a diol. An exemplary' polyol of this type is described in U. S. Patent Pub. No. 2016 / 0090510 (filed Nov. 30, 2015) and incorporated fully herein by reference.[00551 In an embodiment, the polyol described herein has a theoretical hydroxyl equivalent weight of about 100 to 400, preferably 150 to 350. In an embodiment, the polyol described herein has a hydroxyl number of about 100 to 400, preferably 150 to 350.[0056} Suitable acids include, without limitation, aliphatic and aromatic monocarboxylic and di carboxylic acids, saturated and / or unsaturated fatty acids, and the like. In an aspect, aliphatic acids used in the preparation of the polyol described herein include monocarboxylic acids, such as, for example, acetic acid, butanoic acid, hexanoic acid, acrylic acid, methacrylic acid, 2-ethyl hexanoic acid, cyanoacrylic acid, crotonic acid, dodecanoic acid, fatty acid dimers, and the like. In another aspect, aliphatic acids used in the preparation of the polyol described herein include dicarboxylic acids such as, for example, succinic acid, glutaric acid, adipic acid, azelaic acid, suberic acid, sebacic acid, decane di-acid, dodecane di-acid, abietic acid, acid dimers, and the like. The aliphatic acidsAttorney Docket No. 104876-1001may be straight-chain or branched acids. In yet another aspect, aromatic acids used in the preparation of the polyol described herein include aromatic monocarboxylic acids, such as, without limitation, alkyl substituted aromatic acids, alkenyl substituted aromatic acids, or hydroxy substituted aromatic acids. Examples include benzoic acid, hydroxy benzoic acid, cinnamic acid, and the like. In another aspect, aromatic acids include dicarboxylic acids such as, for example, isophthalic acid, terephthalic acid, phthalic acid, naphthalene dicarboxylic acid, 1,4-cyclohexane dicarboxylic acid (CHDA), oxy dibenzoic acid and the like.

[0057] Suitable diols include, without limitation, aliphatic diols selected from unsubstituted or alkyl-substituted aliphatic diols. In an aspect, the diols include, for example, ethylene glycol, di ethylene glycol, tri ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, pentanediol, hexanediol, trimethylol propane, glycerol, and the like. In an embodiment, an unsubstituted diol, preferably 1,4-butanediol, is used.

[0058] In an embodiment, the polyol described herein is the product of a reaction between an epoxide or epoxy-functional compound with an acid or diol. This reaction is carried out in the presence of a reaction catalyst. Suitable catalysts include trialkyl amines, monoalkyl diaryl amines, dialkylaryl amines, triary l amines, trialkyl phosphines, monoalkyl diaryl phosphines, dialkyl aryl phosphines, trialkyl phosphines, quaternary ammonium compounds, quaternary phosphonium compounds, alkali metal halides, and the like. Quarternary7ammonium or phosphonium compounds, and dialkyl aryl amines are preferred. In a preferred embodiment, the reaction catalyst is preferably present in an amount of at least 0.01 wt-%, and more preferably at least 0.1 wt-%, based on the weightAttorney Docket No. 104876-1001of nonvolatile material in the coating composition. The reaction catalyst is preferably present in an amount of no greater than 3 wt-%, and more preferably no greater than 1 wt-%, based on the weight of nonvolatile material in the coating composition.

[0059] In an embodiment, the polymer resin binder system is present in an amount of about 40 to 95 %, preferably about 50 to 80%, and more preferably about 60 to 70 % by¬ weight, based on the total weight of the composition.

[0060] In an aspect, the coating composition described the resin component is selfcrosslinking, and in another aspect, the resin component is crosslinkable with an optional crosslinking agent reactive with the functional group(s) of the resin component.

[0061] Suitable optional crosslinking agents for use in the compositions and method described herein include, for example, aminoplast resins, polyisocyanates, polyepoxides, polyacids and polyamines, combinations or mixtures thereof, and the like. The choice of particular crosslinker typically depends on the particular product being formulated.

[0062] In an embodiment, the optional crosslinking agent is hydroxyl-reactive. In a preferred aspect, the optional crosslinking agent is phenoplasts, aminoplast, isocyanate-functional compounds, dianhydrides, or mixtures thereof.

[0063] Suitable phenoplast resins include the condensation products of aldehydes with phenols. Formaldehyde and acetaldehyde are preferred aldehydes. Various phenols can be employed such as phenol, cresol, p-phenylphenol, o-tert-butylphenol, p-test-butylphenol, p-tert-amylphenol, cyclopentylphenol, and the like.Attorney Docket No. 104876-1001

[0064] Examples of aminoplast resins are the condensation products of aldehydes such as formaldehyde, acetaldehyde, crotonaldehyde, furfural, benzaldehyde, and the like, with amino- or amido-group-containing substances such as urea, melamine, and benzoguanamine. Examples of suitable aminoplast crosslinking resins include, without limitation, benzoguanamine-formaldellyde resins, melamine-formaldehyde resins, etherified melamine-formaldehyde, and urea-formaldehyde resins.J0065] Suitable isocyanate-functional compounds include, without limitation, blocked or unblocked aliphatic, cycloaliphatic or aromatic di-, tri-, or poly-yalent isocyanates, such as hexamethylene diisocyanate, isophorone diisocyanate and the like. Further non-limiting examples of generally suitable unblocked or blocked isocyanates include isomers of isophorone diisocyanate, dicyclohexylmethane diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, phenylene diisocyanate, tetramethyl xylene diisocyanate, xylylene diisocyanate, and mixtures thereof. In some embodiments, unblocked or blocked isocyanates are used that have an Mn of at least about 300. more preferably at least about 650, and even more preferably at least about 1,000.[0066| In an embodiment, where the resin component is self-crosslinking, no additional crosslinking agent is required, but one or more crosslinking agents may still be used. In another embodiment, the crosslinking agent is present in an amount from about 10 to 60 wt. %, preferably 20 to 50 wt. %, and more preferably 30 to 40 wt. %, or any value therebetween, based on the total weight of the composition.

[0067] The composition described herein further includes an organotin-free and / or chrome-free corrosion inhibitor, or a corrosion inhibitor that is free of both organotin and chrome. Suitable corrosion inhibitors for use in the compositions and methods describedAttorney Docket No. 104876-1001herein preferably include inorganic bismuth-containing compounds, preferably multivalent bismuth salts of various anions, more preferably bismuth salts of metal oxy anions. These compounds include their anhydrous forms, as well as various hydrates, including hemihydrate, pentahydrate and other hydrated forms, along with mixtures and combinations thereof, and the like.[00681 In some embodiments, the solar reflective corrosion inhibiting compounds disclosed herein may be used in combination with other known chrome-free or chromate-containing corrosion inhibitors, including a wide range of commercially available powdered pigments and fdlers that behave as corrosion inhibitors. Suitable additional and / or optional corrosion inhibitors include, for example, phosphates or polyphophates, molybdates, borates, silicates, sulfur salts and phosphites of Zn, Ca, Sr, Ba, Al, Mg, Pb, Cr, Fe, or various combinations of these anionic and cationic species. Other active corrosion inhibiting pigments include, for example, organic compounds with SH functionality, such as sulfur salts, thiols, derivatives of dithiocarbonic, dithiocarbamic and dithiophosphoric acids, and the like.

[0069] Other additive compounds may optionally be included in the coating compositions described herein, depending on the substrate and application of interest. Examples of these include one or more defoaming aids, grinding aids, wetting agents, surfactants, coalescing aids, processing aids, skid resistance agents, abrasion resistance agents, conductive agents, antistatic agents, coloring agents, anticorrosion aids, thickeners, sag resistant agents, plasticizers, antioxidants, ultraviolet stabilizers, biocides, fungicides, fdlers, curing agents, or any combination thereof. These can be used in accordance with conventional practices currently known or hereafter developed.Attorney Docket No. 104876-1001

[0070] The coating compositions described herein are suitable for application on a variety of substrates to provide corrosion-resistant coatings, particularly metal or metal alloy substrates. Non-limiting examples of metal substrates that may benefit from having a coating composition of the invention applied on a surface thereof include metal substrates that have a sacrificial metal or alloy coated over steel by processes known un the art, such as electrodeposition or hot dip galvanization, for example. Suitable examples of substrates include, without limitation, hot-rolled steel, cold-rolled steel, hot-dip galvanized, electrogalvanized, aluminum, tin plate, various grades of stainless steel, and aluminum-zinc alloy coated sheet steel (e.g., GALVALUME sheet steel), zinc magnesium steel (e g., ZAM steel), and the like. The coating composition described herein may be applied as a primer coat directly to a bare untreated substrate, or applied over a pretreated substrate. The disclosed coatings can additionally be formulated for base coat and top coat formulations.

[0071] The coating composition described herein, when applied as a primer coat over a bare or pretreated surface, can be applied at a standard dry film thickness of about 1 pm to 200 pm, or 1 pm to 150 pm, 1 pm to 100 pm, or 1 pm to 50 pm, or 1 pm to 10 pm, or 2 pm to 9 pm, or 3 pm to 8 pm, or preferably 4 pm to 7 pm. The primer coat may optionally have a base coat or topcoat applied thereon, with dry film thickness determined by the end use of the coating or coated substrate. In other embodiments, the primer coat is applied at a dry film thickness of 1 mil to 100 mil, or 1- 900 mil, or 1-800 mil, or 1-700 mil, or 1-600 mil, or 1-500 mil or 1-400 mi, or 1-300 mil, or 1-200 mil, or 1-100 mil or any range or value therebetween.

[0072] Also disclosed are methods of inhibiting corrosion on a substrate. The disclosed methods include, providing at least one corrosion-inhibiting compound having aAttorney Docket No. 104876-1001TSR of 40% greater and a HOMO-LUMO bandgap of about 2.2-4.0 eV, incorporating the at least one corrosion-inhibiting compound in a polymeric resin binder system to yield a corrosion-inhibiting coating composition, and applying the corrosion-inhibiting coating composition on the substrate.

[0073] The HOMO-LUMO bandgap of a compound of interest can be determined by currently known methods, including optical spectroscopy and cyclic voltammetry or differential pulse voltammetry.EXAMPLES

[0074] Example 1: Preparation and Application of Coating Compositions

[0075] Coating compositions were prepared by combining an epoxy polymer resin binder component, an amine crosslinker, and the solar reflective pigment. The solar reflective corrosion inhibitor compound was incorporated at a 5.0 weight % of the total weight of the coating composition. The coating composition was applied to cold-rolled steel (CRS) panels using standard application methods at a dry' film thickness of about 1-1.5 mil., and cured at a temperature of 150 °F.

[0076] For comparison, a commercial primer composition that includes a blend of non-chromate corrosion inhibitors was applied over a cold-rolled steel (CRS) substrate (positive control, shown on the left in Fig. 1), and a primer composition without corrosion inhibition components (replaced with inert filler) was applied on a CRS substrate (negative control sample, shown as the middle panel of Fig. 1). The solar reflective (SR) pigment containing primer composition (shown on the right in Fig. 1), was coated on the same substrate. For the results depicted in Fig. 1, the SR pigment was zinc titanate.Attorney Docket No. 104876-1001J0077] Example 2: Accelerated Cyclic Corrosion Testing (SAE J2334 Test Method)10078] Cyclic corrosion tests were performed according to SAE J2334 test method for 60 to 80 cycles (results shown in Figs. 1-3). Each cycle according to SAE J2334 method occurs in a 24 hour period. At a beginning of a cycle, the coated sample substrates are exposed to 6 hours of high humidity (direct fog, 100% RH at 50 °C) followed by salt application by salt solution spray at ambient conditions for 15 minutes, then the samples are dried off at 60 °C for 17 % hours (at 50% RH). The concentration of the salt solution spray is 0.5% NaCl, 0.1% CaCl2, 0.075% NaHCO3.

[0079] For the results shown in Fig. 1, 60 cycles were performed. The results shown in Figs 2 and 3, 80 cycles were performed. Cobalt titanate, bismuth vanadate, bismuth oxide, were investigated on CSR substrates, as described in Example 1-2. In initial studies shown in Fig. 1, it was found that zinc titanate at a loading of 5% w as able to provide improved corrosion inhibition compared to the negative formula which had no included inhibitors. Of interest to note, the positive control in this study contained a blend of commercially available inhibitors and is optimized for performance in SAE J2334. In comparison to the positive control, the zinc titanate had slightly more corrosion at the scribe area, however the 5% loading was not yet optimized to deliver the maximum performance at that point in time. Fig. 2 shows an expanded study with longer duration of corrosion testing; the positive and negative controls in Figs. 1-3 are all identical formulations. In Fig 2. The top performance after 80 cycles of testing was cobalt titanate where superior corrosion inhibition at the artificial defect was observed compared to even the positive control formula.Attorney Docket No. 104876-1001

[0080] For corrosion inhibition on aluminum 2024-T3 substrates, cobalt titanate, bismuth vanadate, and bismuth oxide were tested, as described in Examples 1-2, with 80 cycles of corrosion testing. The results are shown in Fig. 3 where the top performing inhibitor was the bismuth aluminate at 5% loading. Of special note, the bismuth aluminate was able to provide for a decreased in white corrosion product formation in the scribe area with approximately 40% of the scribe area displaying shiny, uncorroded aluminum

[0081] Example 3: Cyclic Polarization Testing10082 ] Cyclic polarization is performed by measuring the open circuit potential of a system and then applying both a cathodic and anodic sweep in the forward and reverse directions. The resulting current is measured and provides both qualitative (shape of hysteresis loop) and quantitative (Ecorr, Esec, min / max current) corrosion data.

[0083] In cyclic polarization experiments, the solar reflective compounds showed substantial increases in passivity and promoted the repassivation of aluminum in 5% NaCl (as shown in Figs. 4 through 15. The corrosion current maximum was reduced for most compounds, and in all cases, there was a positive AE value, a metric correlated with a higher rate of repassivation, and lower corrosion calculated by subtracting the corrosion potential (Ecorr) from the secondary corrosion potential (Esec). The AE of the experimental inhibitors (Esec - Ecorr) was positive in each of the inhibitors (see Figs. 17 and 18). showing that all promoted the repassivation of the aluminum substrate.

[0084] Those skilled in the art will understand from the foregoing description that modifications and changes may be made in various embodiments of the present disclosureAttorney Docket No. 104876-1001without departing from its true spirit of the invention. The descriptions in this specification are for purposes of illustration only and are not to be construed in a limiting sense.

Claims

Attorney Docket No. 104876-1001CLAIMSWhat is claimed is:

1. A coating composition comprising:- a polymeric resin binder system;- at least one corrosion-inhibiting compound having a total solar reflectance (TSR) of about 40% or greater and a HOMO-LUMO band gap of about 2.2 to 4.0 eV.

2. The coating composition of claim 1, wherein the at least one corrosioninhibiting compound comprises at least one solar reflective pigment.

3. The coating composition of claim 1, wherein the at least one corrosioninhibiting compound is selected from bismuth copper oxide (Bi2CuO4), bismuth oxide (BiO3), bismuth manganese oxide, bismuth oxyhalide, bismuth vanadate (BiVO4), manganese iron oxide, yttrium indium manganese oxide, and cobalt titanate (Co2TiO6), cobalt aluminate, cobalt chromite, chromium green-black hematite, zinc titanate, niobium sulfur tin zinc oxide, and ferric ammonium ferrocyanide or a combination thereof.

4. The coating composition of claim 1, wherein the coating composition is a primer coat, a base coat, a topcoat, or a single coat direct to metal formulation.Attorney Docket No. 104876-10015. The coating composition claim 1, wherein the at least one corrosion-inhibiting compound is present in an amount of 0.5 - 20 wt. % based on the total weight of the coating composition.

6. The coating composition of claim 5, wherein the at least one corrosioninhibiting compound is present in an amount of about 0.5-10 wt. %based on the total weight of the coating composition.

7. The coating composition of claim 1, wherein the polymeric resin binder system comprises a polymeric resin and a crosslinking agent.

8. The coating composition of claim 7, wherein the polymeric resin is selected from polyesters, modified polyesters, polyurethanes, polyacrylates, epoxies, modified polyacrylates, and / or combinations thereof.

9. A coated article, comprising:a substrate;a coating composition applied on the substrate, wherein the coating composition comprises;a polymeric resin binder system; andat least one corrosion-inhibiting compound having a total solar reflectance of about 40% or greater and a HOMO-LUMO band gap of about 2.2 to 4.0 eV.Attorney Docket No. 104876-100110. The coated article of claim 9, wherein the at least one corrosion-inhibiting compound comprises at least one solar reflective pigment.

11. The coated article of claim 9, wherein the at least one corrosion-inhibiting compound is selected from bismuth copper oxide (Bi2CuO4), bismuth oxide (BiO3), bismuth oxy halide, bismuth vanadate (BiVO4), cobalt titanate (Co2TiO6), cobalt aluminate, cobalt chromite, chromium green-black hematite, zinc titanate, niobium sulfur tin zinc oxide, and ferric ammonium ferrocyanide or a combination thereof.

12. The coated article of claim 9, wherein the coating composition is a primer coat, a base coat, or a topcoat formulation.

13. The coated article of claim 9. wherein the at least one corrosion-inhibiting compound is present in an amount of 0.5 - 20 wt. % based on the total weight of the coating composition.

14. The coated article of claim 13, wherein at least one corrosion-inhibiting compound is present in an amount of about 0.5-10 wt. % based on the total weight of the coating composition.

15. The coated article of claim 9. wherein the polymeric resin binder system comprises a polymeric resin and a crosslinking agent.Attorney Docket No. 104876-100116. The coated article of claim 9, wherein the polymeric resin is selected from polyesters, modified polyesters, polyurethanes, polyacrylates, epoxies, modified polyacrylates, and / or combinations thereof.

17. The coated article of claim 9, wherein the substrate is a metallic substrate.

18. The coated article of claim 9, wherein the coating is a primer coating having a dry film thickness of 1.0 to 200 pm.

19. The coated article of claim 9, wherein the coating is a primer coating having a dry film thickness of 1-1000 mils.

20. A method of inhibiting corrosion on a substrate, the method comprising:- providing at least one corrosion-inhibiting compound having total solar reflectance of 40% or greater and a HOMO-LUMO bandgap of about 2.2-4.0 eV;- incorporating the at least one corrosion-inhibiting compound in a polymeric resin binder system to yield a corrosion-inhibiting coating composition;- applying the corrosion-inhibiting coating composition on the substrate.

21. The method of claim 20, wherein the at least one corrosion-inhibiting compound comprises at least one solar reflective pigment.Attorney Docket No. 104876-100122. The method of claim 20, wherein the at least one corrosion-inhibiting compound is selected from bismuth copper oxide (Bi2CuO4), bismuth oxide (BiO3), bismuth oxyhalide, bismuth vanadate (BiVO4), cobalt titanate (Co2TiO6), cobalt aluminate, cobalt chromite, chromium green-black hematite, zinc titanate, niobium sulfur tin zinc oxide, and ferric ammonium ferrocyanide or a combination thereof.

23. The method of claim 20, wherein the coating composition is applied to a pretreated or untreated metal substrate, as a primer coating.

24. The method of claim 20, wherein the at least one corrosion-inhibiting compound is present in the corrosion-inhibiting coating in an amount of 0.5 - 20 wt. % based on the total weight of the corrosion-inhibiting coating.

25. The method of claim 24, wherein the at least one corrosion-inhibiting compound is present in the corrosion-inhibiting coating in an amount of 0.5-10 wt. % based on the total weight of the corrosion-inhibiting coating.

26. The method of claim 20, wherein the polymeric resin binder system comprises a polymeric resin and a crosslinking agent.

27. The method of claim 26, wherein the polymeric resin is selected from polyesters, modified polyesters, polyurethanes, polyacrylates, epoxies, modified poly acrylates, and / or combinations thereof.Attorney Docket No. 104876-100128. The method of claim 20, wherein the corrosion-inhibiting coating composition is a primer coating applied at a dry film thickness of 1.0 to 200 pm.

29. The method of claim 20, wherein the coating is a primer coating having a dry film thickness of 1-1000 mils.

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