Powder coating composition containing zinc, coated articles and coated vehicle suspension springs prepared therefrom

Abstract

Powder coating compositions are provided comprising: a) zinc metal in an amount of at least 20 percent by weight and less than 50 percent by weight; b) a resinous binder component in an amount from 35 percent by weight to 77 percent by weight, based on total weight of the powder coating composition; and c) micronized rubber particles in an amount from 3 percent by weight to 15 percent by weight, based on total weight of the powder coating composition. The micronized rubber particles demonstrate a particle size smaller than ASTM E11 Test Sieve Size 200 mesh (74 microns). Also provided are coated articles, in particular, coated vehicle suspension springs, comprising: a) a substrate; and b) a coating layer formed from the powder coating composition described above applied to at least a portion of the substrate. The substrate comprises steel in the coated vehicle suspension spring.

Description

POWDER COATING COMPOSITION CONTAINING ZINC, COATED ARTICLES AND COATED VEHICLE SUSPENSION SPRINGS PREPARED THEREFROM FIELD

[0001] The present disclosure relates to zinc-containing powder coating compositions for improving the corrosion resistance of substrates and coated articles prepared therefrom, in particular, coated vehicle suspension springs.BACKGROUND

[0002] Powder coatings are applied to metal substrates to provide numerous beneficial properties including corrosion protection and decoration. Powder coatings typically comprise an extruded polymer, which is solidified and then ground or milled into a powder. The powder may be electrostatically spray-applied to a substrate and subsequently cured to form a coating layer.

[0003] Vehicular suspension systems are often exposed to highly corrosive environments, most notably in climates where salt is used on road surfaces on a frequent basis, for ice mitigation. So-called “high tensile strength” steel suspension springs, which provide necessary strength at a reduced mass (desirable for fuel economy) are susceptible to such corrosion. They are also harder than springs used previously and are subject to higher internal stresses than normal springs. These factors render them susceptible to breakage as a result of corrosion, because even a small amount of metal loss can lead to a significant reduction in their structural integrity. Additionally, high tensile steel suspension springs are very sensitive to scratches and thus require protection from impact damage due to airborne gravel and stones. Zinc-containing, i. e., “zinc-rich” powder coatings have been used to address these drawbacks.

[0004] High performance, zinc-rich primers usually have high levels (80% loadings by weight or greater) of zinc metal. In powder coatings, these primers, while having excellent performance in corrosion testing, suffer from several issues such as limitations with respect to resin systems that may be used (e. g., the use of two or more different resins may compromise the corrosion resistance) and highcost due to cost per volume and difficulty in application due to the heavy weight of the coating.SUMMARY

[0005] It would be desirable to provide low zinc weight compositions that do not reduce performance versus a higher loading zinc coating composition, and that allow for composition latitude with respect to resin composition.

[0006] The present disclosure provides powder coating compositions comprising: a) zinc metal in an amount of at least 20 percent by weight and less than 50 percent by weight, based on total weight of the powder coating composition; b) a resinous binder component in an amount from 35 percent by weight to 77 percent by weight, based on total weight of the powder coating composition; and c) micronized rubber particles in an amount from 3 percent by weight to 15 percent by weight, based on total weight of the powder coating composition; wherein the micronized rubber particles demonstrate a particle size smaller than ASTM E11 Test Sieve Size 200 mesh (74 microns), as determined using ASTM test method D-5644-18.

[0007] Also provided are coated articles, in particular, coated automotive springs, comprising:a) a substrate; andb) a coating layer formed from the powder coating composition described above, applied to at least a portion of the substrate. The substrate comprises steel in the coated automotive spring.DETAILED DESCRIPTION

[0008] For purposes of the following detailed description, it is to be understood that the disclosure may assume alternative variations except where expressly specified to the contrary. Moreover, other than in any operating examples, or where otherwise indicated, all numbers expressing, for example, quantities of ingredients used in the specification and claims are to be understood as being modified in all instances by the term “about”. Accordingly, unless indicated to thecontrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties to be obtained by the present disclosure. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0009] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the disclosure are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard variation found in their respective testing measurements.

[0010] Also, it should be understood that any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of “1 to 10” is intended to include all sub-ranges between (and including) the recited minimum value of 1 and the recited maximum value of 10, that is, having a minimum value equal to or greater than 1 and a maximum value of equal to or less than 10.

[0011] In this disclosure, the use of the singular includes the plural and plural encompasses singular, unless specifically stated otherwise. Thus, the use of “a” or “an” means “at least one” unless specifically stated otherwise. For example, “a” polymer, “a” pigment, and the like refer to one or more of any of these items.

[0012] The powder coating compositions of the present disclosure comprise a) zinc metal, such as particulates in the form of zinc flakes and / or zinc particles. For example, the zinc metal particulates may be present in at least two physical forms including zinc flakes. In this disclosure, the term “zinc metal” relates to zinc in metallic form, as opposed to, for example, zinc in an oxidized state; the term “form” relates to zinc metal particulates present in different morphologies, including but not limited to particles (e. g., dust and / or powder), or substantially cylindrical, flake or flake-like, substantially planar, and other different shapes. Note that the phrase “and / or” when used in a list is meant to encompass alternative embodiments including each individual component in the list as well as any combination ofcomponents. For example, the list “A, B, and / or C” is meant to encompass seven separate embodiments that include A, or B, or C, or A + B, or A + C, or B + C, or A + B + C.

[0013] The term “zinc powder” as used herein is used interchangeably with the term “zinc dust” and refers to pulverized metallic zinc in granular or substantially spherical form as particles. Zinc powder is an effective and low-cost alternative to galvanized metal. Its particle size allows for excellent adhesion of subsequently applied coating compositions such as topcoats, while galvanizing generally requires pretreatment such as acid etching or wash primers to provide adequate adhesion. The zinc particles average particle size may be at least 1 micron, 2 microns, 3 microns, 4 microns, 4.5 microns, 5 microns, 6 microns, 7 microns, 8 microns, 9 microns, 10 microns, 15 microns, 20 microns, or at most 50 microns, 45 microns, 40 microns, 35 microns, 30 microns, 25 microns, or any range including any two of these values as endpoints. Exemplary ranges include 5 to 50 microns, or 5 to 45 microns, or 5 to 40 microns, or 5 to 35 microns, or 5 to 30 microns, or 5 to 25 microns, or 10 to 50 microns, or 10 to 45 microns, or 10 to 40 microns, or 10 to 35 microns, or 10 to 30 microns, or 10 to 25 microns, or 15 to 50 microns, or 15 to 45 microns, or 15 to 40 microns, or 15 to 35 microns, or 15 to 30 microns, or 15 to 25 microns. Suitable zinc particles are available from Purity Zinc Co., the Zinc Corporation of America (ZCA), or U.S. Zinc. Particle sizes may be determined using ASTM B330-20, which provides procedures for determining the envelope-specific surface area of powders, from which is calculated an “average” particle diameter, assuming the particles are monosize, smooth surface, nonporous, spherical particles. Values obtained by these test methods are reported as an average particle size or Fisher Number.

[0014] The term “zinc flakes” as used herein relates to zinc particulates that are substantially planar or fibrous in shape with an aspect ratio of width to thickness of as little as 1.5:1, 2:1 , 3:1, 4:1 , 5:1 , 6:1 , 7:1 , 8:1, 9:1 , 10:1 , 15:1, or as great as 20:1 , 25:1 , 30:1 , 35:1 , 40:1 , 45:1 , 50:1 , or any range including any two of these values as endpoints. Using zinc flakes in combination with zinc particles in the coating film provides more points of contact between the individual zinc flake and zinc particles. This increased contact promotes sacrificial corrosion of the zincparticles, which may slow the corrosion of the underlying substrate. Suitable zinc flakes typically demonstrate a D50 particle size of 10 to 50 microns determined by laser diffraction. Suitable zinc flakes include Benda-Lutz Z2031, sold by Benda-Lutz of Sun Chemical Group, with a reported D50 particle size of 10 to 30 microns determined by laser diffraction, and ProFlake Zn 2000, with a reported D50 particle size of 15 to 30 microns, available from Eckart America Corp. In certain examples, the powder coating composition does not contain zinc flakes.

[0015] The total zinc metal content of the powder coating compositions may be at least 20 percent by weight, or at least 25 percent by weight, or at least 30 percent by weight and less than 50 percent by weight, or less than 45 percent by weight, or less than 40 percent by weight, based on the total weight of the powder coating composition. For example, the zinc metal may be present in the powder coating composition in an amount of at least 20 and less than 50 percent by weight, or at least 20 and less than 45 percent by weight, or at least 20 and less than 40 percent by weight, or at least 25 and less than 50 percent by weight or at least 25 and less than 45 percent by weight, or at least 25 and less than 40 percent by weight, or at least 30 and less than 50 percent by weight or at least 30 and less than 45 percent by weight, or at least 30 and less than 40 percent by weight, based on the total weight of the powder coating composition.

[0016] The zinc flakes may be present in the coating composition in an amount of at least 10 and less than 40 percent by weight, such as 10 to 35 percent by weight, or 10 to 20 percent by weight, based on the total weight of the powder coating composition, with the remainder of the zinc metal in at least one different physical form. For example, the weight ratio of zinc flakes to zinc in other physical forms may range from 1 :4 to 4:1 , such as 1 :3 or 1 :2 or 1 :1 or 2:1 or 3:1 .

[0017] The powder coating compositions further comprise b) a resinous binder component, which comprises a film-forming resin. As used herein, a “film-forming resin” refers to a resin that may form a self-supporting continuous film on at least a horizontal surface of a substrate upon curing.

[0018] Suitable film-forming resins include (meth)acrylate resins, polyurethanes, polyesters, polyamides, polyethers, polysiloxanes, epoxy resins, vinyl resins, copolymers thereof, and combinations thereof. As used herein, "(meth)acrylate"and like terms refers both to the acrylate and the corresponding methacrylate. The term “polymer” refers to oligomers, homopolymers (e. g., prepared from a single monomer species), copolymers (e. g., prepared from at least two monomer species), terpolymers (e. g., prepared from three monomer species), and graft polymers. Further, the film-forming resins may have any of a variety of functional groups including, but not limited to, carboxylic acid groups, amine groups, epoxide groups, hydroxyl groups, thiol groups, carbamate groups, amide groups, urea groups, isocyanate groups (including blocked isocyanate groups), and combinations thereof.

[0019] Epoxide functional resins (“epoxy resins”) are used most often, and may be used in combination with other resins such as polyester resins. The epoxy resin is typically a polyepoxide comprising at least two or at least three epoxide functional groups. The epoxide functional groups can be terminal and / or pendant on the polymer chain. As used herein, a "pendant group" refers to a functional group that is attached to and extends out from the backbone of a polymer. The epoxy resin can also include any of the additional functional groups previously described. For example, the epoxy resin can include at least one hydroxyl group. The hydroxyl groups, as well as any of the other additional functional groups, can be terminal and / or pendant on the polymer chain. Non-limiting examples of epoxy resins include diglycidyl ethers of Bisphenol A, polyglycidyl ethers of polyhydric alcohols, polyglycidyl esters of polycarboxylic acids, and combinations thereof. Non-limiting examples of suitable epoxy resins are also commercially available from NanYa Plastics under the trade name NPES-903, and from Hexion under the trade names EPON™ 1001 F, EPON™ 2002, EPON™ 1007F and EPON™ 2004.

[0020] The epoxy resin can have an equivalent weight of at least 450 g / equivalent, or at least 500 g / equivalent, and up to 5100 g / equivalent, or up to 1000 g / equivalent, or up to 550 g / equivalent. For example, the epoxy resin can have an equivalent weight range of 450 to 5100 g / equivalent, or 500 to 5100 g / equivalent, or 450 to 1000 g / equivalent, or 500 to 1000 g / equivalent, or 450 to 550 g / equivalent, or 500 to 550 g / equivalent. Epoxy equivalent weight may be determined using ASTM D1652-11 (2019).

[0021] Further, the epoxy resin can have a weight average molecular weight of at least 500 Da, or at least 900 Da, or at least 1000 Da. The epoxy resin can have a weight average molecular weight of up to 11000 Da, or up to 2000 Da, or up to 1000 Da. For example, the epoxy resin can have a weight average molecular weight of 500 to 11000 Da, or 900 to 11000 Da, or 1000 to 11000 Da, or 500 to 2000 Da, or 900 to 2000 Da, or 1000 to 2000 Da, or 500 to 1000 Da, or 900 to 1000 Da. The weight average molecular weight may be determined by gel permeation chromatography relative to linear polystyrene standards of 800 to 900,000 Daltons, as measured with a Waters 2695 separation module with a Waters 410 differential refractometer (Rl detector). Tetrahydrofuran (THF) is used as the eluent at a flow rate of I ml min-l, and two PLgel Mixed-C (300x7.5 mm) columns used for separation.

[0022] The film-forming resin in the resinous binder component b) can comprise two or more epoxy resins as film-forming resins. For example, the film-forming resin can include at least two separate and distinct epoxy resins in which each epoxy resin independently comprises at least two epoxide functional groups and, optionally, any of the other functional groups previously described, such as one or more hydroxyl groups. The multiple epoxy resins can have the same or different equivalent weights. For instance, a first epoxy resin can have an equivalent weight that is greater than an equivalent weight of a second epoxy resin.

[0023] In particular examples the film-forming resin in the resinous binder component b) comprises a “low molecular weight” epoxy resin; i. e., an epoxy resin that demonstrates a weight average molecular weight of 500 to 1000 Da, determined by gel permeation chromatography using a polystyrene standard, and an epoxy equivalent weight of 450 to 550 g / equivalent, such as 450 to 525 g / equivalent or 525 to 550 g / equivalent. Commercially available examples of such epoxy resins include EPON™ 1001 F from Hexion Specialty Chemicals, which has a reported weight average molecular weight of 900 Da. The low molecular weight epoxy resin may be present in the powder coating composition in an amount of 5 to 15 percent by weight, such as 5 to 12 percent by weight, based on the total weight of the powder coating composition.

[0024] In particular examples the film-forming resin in the resinous binder component b) comprises a polyester resin. The polyester resin may be prepared using art recognized starting materials and typically has carboxylic acid functional groups. A typical polyester resin may be any that are suitable for use in a powder coating composition.

[0025] The polyester resin may be used in combination with an epoxy resin, such as any of those described above. Such a combination, or mixture, of different types of resins is often called a “hybrid binder”. Historically, it has been impractical to prepare powder coating compositions comprising certain resins such as polyesters, alone or in combination with other resins such as epoxy, when the powder coating composition contained zinc metal. For example, zinc-rich primers that included hybrid binders often demonstrated weaker corrosion performance than comparable zinc-rich primers that contained only the epoxy resin.

[0026] A non-limiting example of a hybrid binder comprises: (i) an epoxy functional resin; and (ii) an acid functional polyester resin reactive with the epoxy functional resin. The acid functional polyester usually demonstrates an acid value of at least 60 mg KOH / g and less than 100 mg KOH / g (e. g., 60 to 100 mg KOH / g), such as less than 80 mg KOH / g (e. g., 60 to 80 mg KOH / g). It is appreciated that the epoxy functional resin and acid functional polyester resin can react to form a hydroxyl functional reaction product.

[0027] When a polyester resin is used in combination with an epoxy resin, the weight ratio of epoxy resin to polyester resin may be from 1 :1 to 1 :11 , such as 3:4, or 1 :4, or 3:11 . In certain examples, the polyester may be present in the powder coating composition in an amount of at least 20 weight %, or at least 30 weight %, or at least 40 weight % of the powder coating composition. In certain examples, the polyester may be present in the powder coating composition in an amount of up to 60 weight % or up to 50 weight % of the powder coating composition, based on the total solids weight of the powder coating composition. In certain examples, the epoxy resin may be present in the powder coating composition in an amount of at least 5 weight %, or at least 10 weight % of the powder coating composition. In certain examples, the epoxy resin may be present in the powder coating composition in an amount of up to 17 weight % of the powder coating composition,based on total weight of the powder coating composition, such that the total filmforming resin (polyester and epoxy resin) is present as noted above in an amount from 35 percent by weight to 77 percent by weight, or 45 to 77 percent by weight, or 50 to 77 percent by weight, or 35 to 70 percent by weight, or 45 to 70 percent by weight, or 50 to 70 percent by weight, or 35 to 60 percent by weight, or 45 to 60 percent by weight, or 50 to 60 percent by weight, based on total weight of the powder coating composition.

[0028] For example, when a polyester resin is used in combination with an epoxy resin, the polyester is typically present in the powder coating composition in an amount of 20 to 60 percent by weight, or 30 to 60 percent by weight, or 40 to 60 percent by weight, or 20 to 50 percent by weight, or 30 to 50 percent by weight, or 40 to 50 percent by weight, based on total weight of the powder coating composition; and the epoxy resin is typically present in the powder coating composition in an amount of 5 to 17 percent by weight, or 10 to 17 percent by weight, based on total weight of the powder coating composition.

[0029] The resinous binder component b) may further comprise a crosslinking agent, selected from any of the crosslinking agents known in the art to react with the functionality of one or more film-forming resins used in the coating composition. As used herein, the term "crosslinking agent", used interchangeably with “crosslinker”, refers to a molecule comprising two or more functional groups that are reactive with other functional groups and that is capable of linking two or more monomers or polymers through chemical bonds. Alternatively, the filmforming resins that form the binder of the coating composition may have functional groups that are reactive with themselves; in this manner, such resins are selfcrosslinking.

[0030] Suitable crosslinkers include phenolic resins, such as EPIKURE P-202 available from Hexion Specialty Chemicals, amino resins, epoxy functional compounds such as triglycidyl isocyanurate, other isocyanurates, beta-hydroxy (alkyl) amides, alkylated carbamates, (meth)acrylates, isocyanates, blocked isocyanates, polyacids, anhydrides, organometallic acid-functional materials, polyamines, polyamides, aminoplasts, carbodiimides, oxazolines, tetrakis(methoxymethyl)glycoluril, hydroxyalkyl urea, and combinations thereof.

[0031] When used, the crosslinker may be present in the coating composition in an amount of 5 to 15 percent by weight, or 5 to 12 percent by weight, or 6 to 15 percent by weight, or 6 to 12 percent by weight, based on the total weight of the powder coating composition.

[0032] The resinous binder component b) including film-forming resins and any crosslinking agents may be present in the powder coating composition in an amount from 35 to 77 percent by weight, or 45 to 77 percent by weight, or 50 to 77 percent by weight, or 35 to 70 percent by weight, or 45 to 70 percent by weight, or 50 to 70 percent by weight, or 35 to 60 percent by weight, or 45 to 60 percent by weight, or 50 to 60 percent by weight, based on the total weight of the powder coating composition.

[0033] The powder coating composition further comprises c) micronized rubber particles. By “micronized” is meant reduced in size to smaller than ASTM E11 Test Sieve Size 200 mesh (i. e., smaller than about 74 microns), or smaller than ASTM E11 Test Sieve Size 270 mesh (i. e., smaller than about 53 microns), or smaller than ASTM E11 Test Sieve Size 325 mesh (i. e., smaller than about 43 microns), by mechanical grinding. Particle sizes may be determined using ASTM test method D-5644-18 (Standard Test Method for Rubber Compounding Materials — Determination of Particle Size Distribution of Recycled Vulcanizate Particulate Rubber). Such micronized rubber particles are typically prepared (repurposed) from used rubber tires. The particles can be prepared by any method known in the art. The rubber may be natural rubber or synthetic rubber, although it is most common for a mixture of natural and synthetic rubbers to be present. The micronized rubber particles may be conductive. Typically, the micronized rubber particles comprise vulcanized rubber, such as vulcanized natural rubber-styrene butadiene rubber. The particles will usually comprise 30 to 90 percent by weight rubber, such as 40 to 75 percent by weight, or 50 to 60 percent by weight, based on the total weight of the micronized rubber particles.

[0034] When sourced from vehicle tires (usually truck and / or passenger car tires), the micronized rubber particles can also incidentally include additives originally present in the vehicle tires, which are well known in the rubber and tire industries. Common additives include carbon black, oil and fillers such as ash or fibers.Carbon black is typically present in an amount of 10 to 50 percent by weight, such as 25 to 35 percent by weight, based on the total weight of the micronized rubber particles. Oil can be present in amount of 5 to 10 percent by weight, based on the total weight of the micronized rubber particles.

[0035] Suitable micronized rubber particles, such as particles of recycled vehicle tires, usually pass through a mesh size of 200 to 350, such as 300. Suitable micronized rubber particles are available from Lehigh Technologies under the name “MicroDyne”, such as MicroDyne 50-TR, MicroDyne 75-TR; or from Edge Rubber under the name Edge Rubber 200 Mesh; or from Shin-Etsu Chemical Co., Ltd. under the name KMP-597, KMP-598, or KMP-402.

[0036] The micronized rubber particles c) are usually present in the powder coating composition in an amount from 3 to 15 percent by weight, or 5 to 15 percent by weight, or 3 to 10 percent by weight, or 5 to 10 percent by weight, based on the total weight of the powder coating composition.

[0037] The powder coating compositions of the present disclosure may further comprise a crosslinking agent, selected from any of the crosslinking agents known in the art to react with the functionality of one or more film-forming resins used in the coating composition. As used herein, the term "crosslinking agent", used interchangeably with “crosslinker”, refers to a molecule comprising two or more functional groups that are reactive with other functional groups and that is capable of linking two or more monomers or polymers through chemical bonds. Alternatively, the film-forming resins that form the binder of the coating composition may have functional groups that are reactive with themselves; in this manner, such resins are self-crosslinking.

[0038] Suitable crosslinkers include phenolic resins, such as EPIKURE P-202 available from Hexion Specialty Chemicals, amino resins, epoxy resins, triglycidyl isocyanurate, beta-hydroxy (alkyl) amides, alkylated carbamates, (meth)acrylates, isocyanates, blocked isocyanates, polyacids, anhydrides, organometallic acid-functional materials, polyamines, polyamides, aminoplasts, carbodiimides, oxazolines, tetrakis(methoxymethyl)glycoluril, hydroxyalkyl urea, and combinations thereof.

[0039] When used, the crosslinker may be present in the coating composition in an amount of 5 to 15 percent by weight, or 5 to 12 percent by weight, or 6 to 15 percent by weight, or 6 to 12 percent by weight, based on the total weight of the powder coating composition.

[0040] The coating compositions as described herein may further comprise carbon nanotubes, such as single-walled carbon nanotubes, for improving the conductivity and edge corrosion performance of the coatings. Single-wall carbon nanotubes are highly flexible and naturally aggregate to form ropes of elongated tubes. The formation of these ropes in the coating allows for high conductivity while keeping the carbon nanotube loading low. A preferred carbon nanotube additive is available under the name MATRIX 809 Beta from Tuball™.

[0041] The carbon nanotubes may have an outer diameter of less than 5 nm, less than 4 nm, less than 3 nm, less than 2 nm, or less than 1 nm. The carbon nanotubes may have a length of 1 micron to 20 microns, such as 2 to 19 microns, or 3 to 18 microns, or 4 to 17 microns, or 5 to 16 microns, or 6 to 15 microns, or 7 to 14 microns, or 8 to 13 microns, or 9 to 12 microns. The length to diameter ratio of the carbon nanotubes may be from 100:1 to 10,000:1 .

[0042] Any particular carbon nanotube or any combination of carbon nanotubes may be present in the coating composition in an amount of 0.001 to 5 percent by weight, or 0.001 to 2 percent by weight, or 0.001 to 1 percent by weight, or 0.001 to 0.5 percent by weight, or 0.01 to 5 percent by weight, or 0.01 to 2 percent by weight, or 0.01 to 1 percent by weight, or 0.01 to 0.5 percent by weight, or 0.1 to 5 percent by weight, or 0.1 to 2 percent by weight, or 0.1 to 1 percent by weight, or 0.1 to 0.5 percent by weight, based on the total weight of the powder coating composition.

[0043] The coating compositions as described herein may further comprise magnesium oxide (MgO) particles. Suitable MgO particles include, for example, MagChem 200AD particles available from Martin Marietta Magnesia Spec LLC, which exhibit a maximum median particle size of 1 .5 microns and a typical median particle size of 1 .2 microns as reported by the manufacturer. The magnesium oxide particles may be present in the coating composition in an amount of 2 to 15 percent by weight, or 2 to 10 percent by weight, or 3 to 15 percent by weight, or 3to 10 percent by weight, based on the total weight of the powder coating composition.

[0044] The powder coating composition may further comprise one or more additional additives known in the art. Such additives may include flow control agents such as PL-200A, an acrylic-modified silica available from Estron Chemical; flow restricting agents; dry flow agents; aluminum oxide; degassing agents; antioxidants; pigments; colorants; optical brighteners; extenders; surface control agents; waxes; catalysts; reaction inhibitors; conductivity enhancers such as the carbon nanotubes mentioned above, and combinations comprising at least one of the foregoing additives, and the like.

[0045] Any additional additive or combination of additional additives may be present in an amount from 0.5 percent by weight to 1 percent by weight, from 0.5 percent by weight to 8 percent by weight, from 0.5 percent by weight to 6 percent by weight, from 0.5 percent by weight to 5 percent by weight, from 1 percent by weight to 5 percent by weight, from 1 percent by weight to 4 percent by weight, or from 1 percent by weight to 2 percent by weight based on the total weight of the coating composition or based on the weight of one component of the coating composition.

[0046] The present disclosure is further drawn to coated articles comprising a) a substrate; and b) a coating layer formed from any of the powder coating compositions described above, applied to at least a portion of the substrate.

[0047] Substrates may include vehicular substrates, such as automotive substrates, industrial substrates, marine substrates and components such as ships, vessels, and on-shore and off-shore installations, storage tanks, packaging substrates, aerospace components, fasteners, coiled metals, heat exchangers, vents, an extrusion, roofing, wheels, grates, belts, conveyors, grain or seed silos, wire mesh, bolts or nuts, a screen or grid, HVAC equipment, frames, tanks cords, wires, electronic components, including housings and circuit boards, sports equipment, stadiums, buildings, bridges, containers such as a food and beverage containers, and the like. As used herein, "vehicle" or variations thereof includes, but is not limited to, civilian, commercial and military aircraft, and / or land vehicles such as airplanes, helicopters, cars, motorcycles, and / or trucks. The shape of thesubstrate can be in the form of a sheet, plate, bar, rod, spring or any shape desired. Often the substrate comprises a vehicle suspension spring.

[0048] The substrates, including any of the substrates previously described, are typically metallic substrates, which are prone to corrosion. Metallic substrates include, but are not limited to, tin, steel, cold rolled steel, hot rolled steel, steel coated with zinc metal, zinc compounds, zinc alloys, electrogalvanized steel, hot-dipped galvanized steel, galvannealed steel, galvalume, steel plated with zinc alloy, stainless steel, zinc-aluminum magnesium alloy coated steel, zincaluminum alloys, aluminum, aluminum alloys, aluminum plated steel, aluminum alloy plated steel, steel coated with a zinc-aluminum alloy, magnesium, magnesium alloys, nickel, nickel plating, bronze, tinplate, clad, titanium, brass, copper, silver, gold, 3-D printed metals, cast or forged metals and alloys, or combinations thereof.

[0049] As noted above, often the substrate comprises a vehicle suspension spring. The present disclosure is thus further drawn to a coated vehicle suspension spring, comprising a) a steel substrate; and b) a coating formed from any of the powder coating compositions described above, applied to at least a portion of the steel substrate.

[0050] In the making of the coated articles such as coated vehicle suspension springs disclosed herein, the components of the powder coating compositions may be combined by mixing, grinding, or any suitable contacting method. The components may be a solid and more specifically may be a powder. The individual components may be contacted in any suitable ratio to form the coating composition.

[0051] The substrate may be preheated to a surface temperature or a bulk temperature before the application of the coating composition. The substrate may be heated to a surface temperature of at least 100 °F, or at least 125 °F, or at least 150 °F, or at least 175 °F, or at least 200 °F, or at most 225 °F, or at most 250 °F, or at most 275 °F, or at most 300 °F, or at most 325 °F, or at most 350 °F, or at most 375 °F, or at most 400 °F. In metric units, the substrate may be heated to a surface temperature of at least 40 °C, or at least 50 °C, or at least 60 °C, or at least 70 °C, or at least 80 °C, or at least 90 °C, or at least 100 °C, or at least110 °C, and at most 120 °C, or at most 130 °C, or at most 140 °C, or at most 150 °C, or at most 160 °C, or at most 170 °C, or at most 180 °C, or at most 190 °C, or at most 200 °C, or at most 210 °C. For example, the substrate may be heated to a surface temperature from 40 °C to 150 °C, from 50 °C to 150 °C, from 60 °C to 150 °C, from 70 °C to 150 °C, from 80 °C to 150 °C, from 90 °C to 150 °C, from 100 °C to 150 °C, from 110 °C to 150 °C, from 110 °C to 140 °C, or from 120 °C to 140 °C.

[0052] Once the coating composition has been applied to the substrate, the coating is cured. The curable coating composition may be cured with heat, increased or reduced pressure, chemically such as with moisture, or with other means such as actinic radiation, and combinations thereof. Curing may comprise an initial curing step with radiation, followed by heating. The term “actinic radiation” refers to electromagnetic radiation that can initiate chemical reactions. Actinic radiation includes, but is not limited to, visible light, ultraviolet (UV) light, infrared (IR), X-ray, and gamma radiation.

[0053] The term "curable", as used for example in connection with a curable composition, means that the indicated composition is polymerizable or cross linkable through functional groups, e.g., by means that may include thermal (including ambient cure) and / or catalytic exposure. Ambient temperature usually ranges from 60 to 90°F (15.6 to 32.2°C), such as a typical room temperature, 72°F (22.2°C).

[0054] The term “cure”, “cured” or similar terms, as used in connection with a cured or curable composition, e.g., a “cured composition” of some specific description, means that at least a portion of the polymerizable and / or crosslinkable components that form the curable composition is polymerized and / or crosslinked through reactive functional groups, to the extent that a cured film prepared from the composition demonstrates no damage from at least 50 methylethyl ketone (MEK) double rubs according to ASTM D5402-19. The test method may be performed, for example, using the specified cheesecloth or another suitable cloth such as a Wypall X80 towel available from Kimberly Clark Corporation. The term “at least partially cured” means subjecting the composition to curing conditions, wherein reaction of at least a portion (e. g., at least 5 percent) of the reactivegroups of the composition occurs, to form a polymerizate. The composition can also be subjected to curing conditions such that a complete cure is attained (for example, greater than 50 percent of reactive groups have reacted) and wherein further curing results in no further improvement in polymer properties, such as hardness.

[0055] The coating composition may be cured at a temperature from 120 °C to 200 °C, from 120 °C to 190 °C, from 120 °C to 180 °C, from 120 °C to 170 °C, from 120 °C to 160 °C, from 120 °C to 150 °C, from 120 °C to 140 °C, or from 120 °C to 130 °C.

[0056] The curing step may be carried out for any suitable time to allow the coating to fully or at least partially cure. The curing time may vary depending on the substrate, the coating composition, the coating thickness, ambient conditions, curing methods, or any combination of these factors. Curing time may be as little as 1 minute, 2 minutes, 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, 10 minutes, or as great as 60 minutes, 55 minutes, 50 minutes, 45 minutes, 40 minutes, 35 minutes, 30 minutes, 25 minutes, 20 minutes, 15 minutes, 12 minutes, or any range including any two of these values as endpoints. The curing time may be from 1 minute to 30 minutes, from 1 minute to 20 minutes, from 1 minute to 15 minutes, from 1 minute to 10 minutes, from 1 minute to 6 minutes, from 5 minutes to 15 minutes, from 5 minutes to 10 minutes, or from 3 minutes to 9 minutes.

[0057] The overall coating on the substrate may have a thickness of at least 0.1 mils, 0.2 mils, 0.3 mils, 0.4 mils, 0.5 mils, 0.6 mils, 0.7 mils, 0.8 mils, 0.9 mils, 1 mil, 1.5 mils, 2 mils, 2.5 mils and / or up to 20 mils, 15 mils, 14 mils, 13 mils, 12 mils, 11 mils, 10 mils, 9 mils, 8 mils, 7 mils, 6 mils, 5 mils, 4 mils, 3.9 mils, 3.8 mils, 3.7 mils, 3.6 mils, 3.5 mils, 3.4 mils, 3.3 mils, 3.2 mils, 3.1 mils, 3 mils, or any range including any two of these amounts as endpoints. For example, the overall coating may have a thickness of 1 mils to 4 mils, 1 .5 mils to 2.5 mils, or 2 mils to 3 mils. The thickness may be measured according to the ASTM D7091-13 test method using and Elcometer 415 Model B Dual FNF film gauge.

[0058] Application methods that can be used to apply the coating composition onto the substrate include: spraying, such as by incorporating the coatingcomposition into a liquid formulation and using spray equipment; media blasting where the coating composition is a solid and is blasted onto the substrate's surface; or electrostatically spray-applied.

[0059] The coating composition may be applied directly to a substrate without any intermediate layers between the coating composition and the substrate. The coating composition may be applied directly to a metal substrate, before or after the substrate is cleaned and / or treated as known in the art, but before application of any coating layers. The coating composition may also be applied during cleaning such as a component of the cleaner. The coating composition may be applied over the entire surface, edges, and corners of the substrate, or the coating composition may be applied over selected portions of the substrate.

[0060] The coating composition may also form a continuous or semi-continuous coating layer over the substrate, or the coating composition may be applied over certain spots / areas of the substrate such as the edges and corners of the substrate. As used herein, the area referred to as the "edge" will vary based on the particular substrate but may include, e.g., the outer most lateral face of the substrate.

[0061] The coating composition can be applied to the substrate to form a monocoat. As used herein, a "monocoat" refers to a single coating layer that is free of additional coating layers. Thus, the coating composition can be applied directly to a substrate and cured to form a single layer coating, i.e. a monocoat.

[0062] The coated articles including coated vehicle suspension springs of the present disclosure may further comprise one or more additional coating layers, such as a topcoat deposited onto at least a portion of the powder coating composition, to form a multi-layer coating. When a multi-layer coating is formed, the powder coating composition can be cured prior to application of additional overcoats, or one or more of the additional overcoats and the powder coating composition can be cured simultaneously. It is appreciated that the additional coating layer(s) can be applied in solid or liquid form. The additional coating layers may be prepared from any suitable coating compositions known in the art. Such coating compositions may contain any of the micronized rubber particles disclosed above. Certain examples of suitable additional coating compositions used for thepreparation of coated vehicle suspension springs include PCM90195, which contains tire rubber (micronized rubber) particles, and PCM90200 and PCTZ39104, which do not contain any rubber particles, all of which are available from PPG. Also suitable as additional coating compositions for the preparation of coated vehicle suspension springs are any of those described in United States Patent Application Publication Number 2017 / 0174906 A1 , incorporated herein by reference in its entirety. Such coating compositions contain tire rubber (micronized rubber) particles.

[0063] Substrates coated according to the present disclosure may have one or more improved properties and may address one or more issues known in the coating industry. The improved properties may be observed in comparison to other, previously known coating compositions, as shown in the working Examples below.

[0064] The powder coating compositions typically demonstrate resistance to corrosion as measured by a salt spraying test according to the methods set forth in GMW14872 Cyclic Corrosion Laboratory Test. The powder coating compositions, when applied to a substrate and cured, may demonstrate less than 12 mm, or less than 10 mm, or less than 5 mm, or less than 3 mm average scribe creepage after at least 100 cycles. Moreover, after application of the powder coating composition and the additional coating composition containing micronized rubber particles to the substrate and after curing the coating compositions, the coated article, such as the coated automotive spring, typically demonstrates improved corrosion resistance when subjected to GMW14872 Cyclic Corrosion Laboratory Test for 100 cycles, compared to an analogous coated article wherein the additional coating composition does not comprise micronized rubber particles. By “analogous” is meant a coated article that is the same as a coated article according to the present disclosure in every respect but for the exception indicated.

[0065] The powder coating compositions of the present disclosure typically demonstrate resistance to corrosion when exposed to a corrosive test environment such as ASTM B117-19, a neutral salt fog exposure test; GMW14872 (2021), a cyclic corrosion exposure test standard developed by General Motors(GM); or SAE J2334 (2016), an automotive standard for cyclic corrosion testing. The powder coating compositions, when applied to a substrate and cured, may demonstrate reduced scribe delamination, as per ASTM D1654-24 Test Method used to evaluate the corrosion resistance of painted substrates after at least 70 cycles GMW14872 or at least 1000 hours of B117-19 exposure. Moreover, after application of the powder coating composition and the additional coating composition containing micronized rubber particles to the substrate and after curing the coating compositions, the coated article, such as the coated automotive spring, typically demonstrates improved corrosion resistance when subjected to GMW14872 for 100 cycles and evaluated as per ASTM D1654, compared to an analogous coated article wherein the additional coating composition does not comprise micronized rubber particles.

[0066] The powder coating compositions typically demonstrate resistance to corrosion as measured by a cyclic corrosion test according to the methods set forth in SAEJ2334. The powder coating compositions of the present disclosure, when applied to a substrate and cured, may demonstrate improved corrosion resistance after at least 40 cycles and evaluated as per ASTM D1654, compared to a similar coated article wherein the additional coating composition does not comprise micronized rubber particles. Moreover, after application of the powder coating composition of the present disclosure and the additional coating composition containing micronized rubber particles to the substrate and after curing the coating compositions, the coated article, such as a coated test panel, typically demonstrates improved corrosion resistance when subjected to SAEJ2334 Test for 40 cycles and evaluated as per ASTM D1654, compared to an analogous coated article wherein the additional coating composition does not comprise micronized rubber particles.

[0067] The present disclosure is thus drawn to the following aspects:1 . A powder coating composition comprising:a) zinc metal in an amount of at least 20 percent by weight and less than 50 percent by weight, based on total weight of the powder coating composition; b) a resinous binder component in an amount from 35 percent by weight to 77 percent by weight, based on total weight of the powder coating composition; andc) micronized rubber particles in an amount from 3 percent by weight to 15 percent by weight, based on total weight of the powder coating composition; wherein the micronized rubber particles demonstrate a particle size smaller than ASTM E11 Test Sieve Size 200 mesh (74 microns) , as determined using ASTM test method D-5644-18.2. The powder coating composition of aspect 1 , wherein the zinc metal comprises zinc flakes and / or zinc particles.3. The powder coating composition of aspect 2, comprising the zinc particles, wherein the zinc particles demonstrate an average particle size of 5 to 50 microns, as determined by ASTM B330-20.4. The powder coating composition of aspect 2 or 3, comprising the zinc particles, wherein the zinc particles demonstrate an average particle size of 10 to 50 microns, as determined by ASTM B330-20.5. The powder coating composition of any of aspects 2 to 4, comprising the zinc particles, wherein the zinc particles demonstrate an average particle size of 15 to 50 microns, as determined by ASTM B330-20.6. The powder coating composition of any of aspects 2 to 5, comprising the zinc particles, wherein the zinc particles demonstrate an average particle size of 5 to 30 microns, as determined by ASTM B330-20.7. The powder coating composition of any of aspects 2 to 6, comprising the zinc particles, wherein the zinc particles demonstrate an average particle size of 10 to 30 microns, as determined by ASTM B330-20.8. The powder coating composition of any preceding aspect, wherein the zinc metal is present in an amount of at least 20 percent by weight and less than 40 percent by weight, based on total weight of the powder coating composition.9. The powder coating composition of any preceding aspect, wherein the zinc metal is present in at least two physical forms including zinc flakes, at a weight ratio of zinc flakes to zinc in other physical forms of 1 :4 to 4:1.10. The powder coating composition of any preceding aspect, wherein the zinc metal is present in at least two physical forms including zinc flakes, and wherein the zinc flakes are present in an amount from 10 percent by weight to 20 percent by weight, based on total weight of the powder coating composition.11 . The powder coating composition of any preceding aspect, wherein the resinous binder component comprises a film-forming resin comprising an epoxy resin and / or a polyester resin.12. The powder coating composition of aspect 11, wherein the film-forming resin comprises the epoxy resin, and wherein the epoxy resin demonstrates a weight average molecular weight of 500 to 1000 Da, determined by gel permeation chromatography using a polystyrene standard, and an epoxy equivalent weight of 450 to 550 g / equivalent, and is present in the powder coating composition in an amount of 5 to 15 percent by weight, based on total weight of the powder coating composition.13. The powder coating composition of aspect 12, wherein the epoxy resin demonstrates an epoxy equivalent weight of 450 to 525 g / equivalent.14. The powder coating composition of aspect 12, wherein the epoxy resin demonstrates an epoxy equivalent weight of 525 to 550 g / equivalent.15. The powder coating composition of aspect 11, wherein the film-forming resin comprises the epoxy resin, and wherein the epoxy resin demonstrates (i) a weight average molecular weight of 500 to 11000 Da, determined by gel permeation chromatography using a polystyrene standard, and / or (ii) an epoxy equivalent weight of 450 to 5100 g / equivalent.16. The powder coating composition of any of aspects 11 to 15, wherein the film-forming resin comprises the epoxy resin and the polyester resin.17. The powder coating composition of any preceding aspect, wherein the resinous binder component further comprises a crosslinking agent selected from phenolic resins, amino resins, epoxy functional compounds, isocyanurates, beta-hydroxy (alkyl) amides, alkylated carbamates, (meth)acrylates, isocyanates, blocked isocyanates, polyacids, anhydrides, organometallic acid-functional materials, polyamines, polyamides, aminoplasts, carbodiimides, oxazolines, tetrakis(methoxymethyl)glycoluril, hydroxyalkyl urea, and combinations thereof.18. The powder coating composition of aspect 17, wherein the crosslinking agent is present in the coating composition in an amount of 5 to 15 percent by weight, based on the total weight of the powder coating composition.19. The powder coating composition of any preceding aspect, wherein the micronized rubber particles are present in an amount of 5 to 15 percent by weight, based on the total weight of the powder coating composition.20. The powder coating composition of any preceding aspect, wherein the micronized rubber particles are present in an amount of 3 to 10 percent by weight, based on the total weight of the powder coating composition.21 . The powder coating composition of any preceding aspect, wherein the micronized rubber particles are present in an amount of 5 to 10 percent by weight, based on the total weight of the powder coating composition.22. The powder coating composition of any preceding aspect, wherein the composition further comprises carbon nanotubes in an amount from 0.001 percent by weight to 5 percent by weight based on total weight of the powder coating composition.23. The powder coating composition of any preceding aspect, wherein the composition further comprises magnesium oxide particles in an amount of 2 to 15 percent by weight, based on total weight of the powder coating composition.24. The powder coating composition of any preceding aspect, wherein the composition further comprises magnesium oxide particles in an amount of 2 to 10 percent by weight, based on total weight of the powder coating composition.25. The powder coating composition of any preceding aspect, wherein the micronized rubber particles are prepared from used rubber tires.26. The powder coating composition of aspect 1, wherein the powder coating composition does not contain zinc flakes.27. A coated article comprising:a) a substrate; andb) a coating formed from the powder coating composition of any preceding aspect, applied to at least a portion of the substrate.28. The coated article of aspect 27, wherein the substrate comprises steel.29. The coated article of aspect 27 or 28, wherein the substrate comprises a vehicle suspension spring.30. The coated article of any of aspects 27 to 29, further comprising an additional coating composition applied to at least a portion of the powder coating composition.31. The coated article of aspect 30, wherein the additional coating composition comprises micronized rubber particles.32. The coated article of aspect 31, wherein the micronized rubber particles prepared from used rubber tires.33. The coated article of any of aspects 31 to 32, wherein after application of the powder coating composition and the additional coating composition to the substrate and after curing the coating compositions, the coated article demonstrates improved corrosion resistance when subjected to GMW14872 Cyclic Corrosion Laboratory Test for 100 cycles, compared to an analogous coated article wherein the additional coating composition does not comprise rubber particles.34. A coated vehicle suspension spring comprising:a) a steel substrate; andb) a coating formed from the powder coating composition of any of aspects 1 to 26 applied to at least a portion of the steel substrate.35. The coated automotive spring of aspect 34, further comprising an additional coating composition applied to at least a portion of the powder coating composition.36. The coated automotive spring of aspect 35 wherein the additional coating composition comprises micronized rubber particles.37. The coated automotive spring of aspect 36, wherein after application of the powder coating composition and the additional coating composition to the steel substrate and after curing the coating compositions, the coated automotive spring demonstrates improved corrosion resistance when subjected to GMW14872 Cyclic Corrosion Laboratory Test for 100 cycles, compared to an analogous coated automotive spring wherein the additional coating composition does not comprise rubber particles.EXAMPLES

[0068] The following working Examples are intended to further describe and demonstrate the compositions, coated articles, and methods described herein. It is understood that the disclosure of this specification is not necessarily limited to the examples described in this section. Components that are mentioned elsewhere in the specification as suitable alternative materials for use, but which are not demonstrated in the working Examples below, are expected to provide results comparable to their demonstrated counterparts. Unless otherwise indicated, all parts are by weight.Examples 1 to 7

[0069] Powder coating compositions were prepared from the components listed below in Table 1. Example 1 is a Control that does not contain rubber particles. Examples 2 to 6 are representative of the powder coating compositions of the present disclosure. Example 7 is comparative in that the composition contains conventional levels of zinc metal (ca. 80 percent by weight), but no zinc flakes.

[0070] Each of the components listed in Table 1 were weighed in a container and mixed in a prism high speed mixer for 15 seconds at 2500 RPM to form a dry homogeneous mixture. The mixture was then melt-mixed in a Werner Pfleiderer 19mm twin screw extruder with an aggressive screw configuration and a speed of 500 RPM. The first zone was set at 50°C, and the second, third, and fourth zones were set at 95°C. The feed rate was such that a torque of 40%-50% was obtained on the equipment for Example 1 and the same feed rate was maintained for the other Examples. The extruded material dropped onto a set of chill rolls to cool and re-solidify the mixtures into solid chips. The post additive listed in Table 1 as aluminum oxide was incorporated with the cooled chips. The chips were milled to a fine powder in a Mikro ACM®-1 Air Classifying Mill to obtain a fine powder that was tap-sieved with a 100-mesh screen to achieve final particle size ranges of 5 to 149 microns, with a majority of the particles from 35 to 45 microns. The resulting coating compositions for each of Examples 1 through 7 were solid particulate powder coating compositions that were free flowing.Table 1Ingredient Ex 1 Ex 2 Ex 3 Ex 4 Ex 5 Ex 6 Ex 7 (Control) (Comparative)EPON 2004130.54 28.96 25.85 23.64 29.32 24.99 8.16 NPES-903211.14 10.56 9.43 2.94 3.65 3.66 8.16 EPON 1001 F3- - - 6.51 8.08 8.11 - EPIKURE P-20249.92 7.08 6.32 8.51 10.56 10.60 3.28 PL-200A50.20 0.20 0.20 0.20 0.20 0.20 0.20 Benzoin60.10 0.10 0.10 0.10 0.10 0.10 0.10 MicroDyne 507- 5.00 10.00 10.00 10.00 10.00 - TUBALL Matrix Beta 0.20 0.20 0.20 0.20 0.20 - - 809s#2 ZINC 33.50 33.50 33.50 33.50 23.50 23.50 80.01 DUST / 330LL109Benda-Lutz Z2O311014.30 14.30 14.30 14.30 14.30 14.30 - Aluminum Oxide110.10 0.10 0.10 0.10 0.10 0.10 0.10Total Grams 100.00 100.00 100.00 100.00 100.00 100.00 100.001 Epoxy resins available from Hexion Specialty Chemicals2 Epoxy resin available from NAN YA PLASTICS3 Epoxy resin available from Miller-Stephenson4 Phenolic curative available from Hexion Specialty Chemicals5 Acrylic polymer modified silica available from Estron Chemical6 2-Hydroxy-2-phenylacetophenone available from Haungshan Linlu Coatings Materials7 Micronized rubber available from Lehigh Technologies8 Graphene nanotubes available from OCSiAL9 Zinc Dust available from U.S Zinc10 Zinc Flake available from Sun Chemical11 AEROX Aluminum Oxide C available from Cabot CorporationApplication and testing

[0071] The Example powder coating compositions in Table 1 were applied with an Encore Nordson powder coating cup gun at 75kV, 15mA, 10 psi atomizing and 10 psi conveying flow air. The coating thickness was 38 microns to 51 microns over CRS C700 C59 test panels available from ACT Test Panels, LLC. The coatings were gelled at 375°F for 5 minutes to form a primer coating layer and allowed to cool. A commercial topcoat available from PPG, PCTZ39104, was applied over the primer compositions with an Encore Nordson powder coating cup gun at 75kV, 15mA, 10 psi atomizing and 10 psi conveying flow air. The topcoat coating thickness was 51 urn to 70um. Both primer and topcoat were cured with a 2O’@ 375°F bake.

[0072] Comparative corrosion testing was done as per GMW14872 Cyclic Corrosion Laboratory Test for 100 cycles. For corrosion testing the panels were cut through to the metal with a carbine tipped pen to the metal substrate down themiddle of the test panels approximately 4 inches on a 6-inch test panel. After testing, the panels were scraped free of loose coating and corrosion products under a warm water flow exposing the area that experienced coating failure. The exposed cleaned area, called scribe creep, was measured as total scribe creep across the exposed area 90° to the scribe line. An average of 10 readings on two panels is reported in millimeters total scribe creep in Table 2.Table 2Ex 1 Ex 2 Ex 3 Ex 4 Ex 5 Ex 6 Ex 7 (Control) (Comparative)14 7 5 6 6 6 5

[0073] As shown in Table 2, when the Control Example 1, a composition containing 47.8% zinc metal and representative of the compositions of WO 2023 / 215677 A1 , was modified with conductive, micronized rubber particles as in Examples 2 and 3, corrosion resistance was improved. Additionally, modifying the composition with a low molecular weight epoxy resin maintained performance, as shown in Example 4. When the composition of Example 4 was additionally modified with less zinc metal, 37.8% zinc, corrosion performance was maintained as shown in Example 5. Performance was also maintained with the removal of carbon nanotubes in Example 6 as compared to Example 5. Over all, Examples 2, 3, 4, 5 and 6 are equal or close to the performance of the comparative composition containing 80% zinc (Example 7), demonstrating the excellent performance of the lower zinc containing compositions and the importance of micronized rubber.Examples 8 to 10

[0074] Each of Examples 8 to 10 comprising the components listed in Table 3 were prepared as above. The resulting coating compositions for each of Examples 8 through 10 were solid particulate powder coating compositions that were free flowing. Example 8 is a control containing no rubber particles; Examples 9 and 10 represent powder coating compositions of the present disclosure.Table 3Ingredient Ex 8 Ex 9 Ex 10 Ex 7(Control) (Comparative)EPON 2004 30.54 25.85 29.32 8.16NPES-903 11.14 9.43 3.65 8.16EPON 1001 F - - 8.08 - EPIKURE P-202 9.92 6.32 10.56 3.28PL-200A 0.20 0.20 0.20 0.20 Benzoin 0.1 0.10 0.10 0.10 MicroDyne 50 - 10.00 10.00 - TUBALL Matrix Beta 809 0.20 0.20 0.20 - #2 ZINC DUST / 330LL10 33.50 33.50 23.50 80.01 Benda-Lutz Z2031 14.30 14.30 14.30 - Aluminum Oxide 0.10 0.10 0.10 0.10Total Grams 100.00 100.0 100.00 100.000

[0075] The Example powder coating compositions in Table 3 were applied as primers with an Encore Nordson powder coating cup gun at 75kV, 15mA, 10 psi atomizing and 10 psi conveying flow air. The coating thickness was between 38um to 51 urn over CRS C700 C59 test panels available from ACT Test Panels, LLC. The coatings were gelled at 375°F for 5 minutes to form a coating layer and allowed to cool. A commercial topcoat available from PPG, PCTZ39104, was applied over the primer compositions with an Encore Nordson powder coating cup gun at 75kV, 15mA, 10 psi atomizing and 10 psi conveying flow air. The topcoat coating thickness was between 51 urn to 70um.

[0076] Additional testing was conducted by applying the Example compositions as primers over steel automotive spring sections, approximately 7-8 inches in length, that were obtained from a spring supplier and pretreated with CHEMFOS 700 zinc phosphate pretreatment composition and Chemseal 59 sealer, both available from PPG. For application, the spring sections were heated to 375°F and the coating compositions were applied with an Encore Nordson powder coating cup gun at 75kV, 15mA, 10 psi atomizing and 10 psi conveying flow air to a coating thickness was between 38um to 51 urn for the coating composition. A commercial topcoat available from PPG, PCM90195, was immediately applied over the primer with the same settings to a film build of 255um to 765um. The spring sections were then baked 2O’@375°F to cure the primer and topcoat coating layers.

[0077] Comparative corrosion testing on the panels was done as per GMW14872 Cyclic Corrosion Laboratory Test for 100 cycles. For corrosion testing the panels were cut through to the metal with a carbine tipped pen to the metal substrate down the middle of the test panels approximately 4 inches on a 6- inch test panel. After testing, the panels were scraped free of loose coating and corrosion products under a warm water flow exposing the area that experienced coating failure. The exposed cleaned area, called scribe creep, was measured as total scribe creep across the exposed area 90° to the scribe line. An average of 10 readings on two panels is reported in millimeters total scribe creep in Table 4 below.

[0078] In preparation for corrosion testing as per GMW14872 Cyclic Corrosion Laboratory Test, the spring sections were scribed utilizing a Dremel tool with a cutting disc attachment cutting through the coating layers down to the metal, approximately 5 inches in length across the length of the 7-8 inch long spring sections. After testing, the spring sections were scraped free of loose coating and corrosion products under a warm water flow with a knife, lifting up and removing any loose coating. The exposed metal and corrosion product, called scribe creep, was measured as total scribe creep across the exposed area 90° to the scribe line. 3 spring sections were measured in ten locations and the average of 30 readings is reported below in mm total scribe creep in Table 4.Table 4Ex 8 Ex 9 Ex 10 Ex 7 (Control) (Comparative) CRS C700 C59 panels, 100 12 9 10 10 Cycles GMW14872 Averagemm Average Scribe CreepAutomotive spring sections 100 8 2 1 3 Cycles GMW14872 mmAverage Scribe Creep

[0079] As shown in Table 4, when the Control Example 8, a composition containing 47.8% zinc and representative of the compositions of WO 2023 / 215677 A1 , is modified with 10% micronized rubber in Example 9, corrosion performance is improved on both panels and automotive spring sections. Performance is also improved in Example 10 with 37.8% zinc and micronized rubber. Overall, theperformance of the low zinc primer compositions is similar to or better than comparative epoxy primer composition containing 80% zinc (Example 7), demonstrating the similar performance of the low zinc containing primer compositions to a standard high level zinc rich primer composition.Examples 11 to 15

[0080] Each of the Examples 11 to 15 comprising the components listed in Table 5 was prepared as above. The resulting coating compositions for each of Examples 11 through 15 were solid particulate powder coating compositions that were free flowing. Example 11 is a control containing no rubber particles; Examples 12 to 15 represent powder coating compositions of the present disclosure.Table 5Ingredient Ex 11 Ex 12 Ex 13 Ex 14 Ex 15 Ex 7 (Control) (Comparative) Epon 2004 30.27 25.57 22.46 28.94 28.94 8.16 NPES-903 11.04 9.33 8.20 3.60 3.60 8.16 Epon 1001F - - - 7.98 7.98 - Epikure P-202 9.83 6.25 5.49 10.43 10.43 3.28 DMLA-P120.10 0.10 0.10 0.10 0.10 - PL-200A 0.30 0.30 0.30 0.30 0.30 0.20 Benzoin 0.50 0.50 0.50 0.50 0.50 0.10 MicroDyne 50 10.00 10.00 10.00 10.00 - Magchem13- - 5.00 - - - TUBALL Matrix Beta 0.20 0.20 0.20 0.20 0.20 - 809#2 ZINC 33.50 33.50 33.50 23.50 23.50 80.01 DUST / 330LL10Benda-Lutz Z2031 14.30 - 14.30 14.30 - - ProFlake Zn 200014- 14.30 - - 14.30 - Aluminum Oxide 0.15 0.15 0.15 0.15 0.15 0.10Total Grams 100.00 100.00 100.00 100.00 100.00 100.00 12 Dimethyl-Dodecylamine available from Danick Specialties & Support Inc. 13 Magnesium oxide particles available from Martin Marietta Magnesia Spec LLC 14 Zinc Flake available from Eckart America Corp.

[0081] The Example powder coating compositions in Table 5 were applied with an Encore Nordson powder coating cup gun at 75kV, 15mA, 10 psi atomizing and10 psi conveying flow air over automotive steel spring sections, approximately 7- 8 inches in length that were obtained from a spring supplier with pretreatment applied by the customer. For application, the spring sections were heated to 375°F and the primer compositions were applied to a coating thickness between 38um to 45um.

[0082] A commercial topcoat available from PPG, PCM90195, which contains conductive rubber particles, or PCM90200, which does not contain any rubber particles, was immediately applied over the primer with the same settings to a film build of 255um to 510um. The spring sections were then baked 2O’@375°F to cure the primer and topcoat coating layers.

[0083] Corrosion testing was conducted as in Examples 8 to 10 above. Results are reported in millimeters total scribe creep in Table 6.Table 6Ex 11 Ex 12 Ex 13 Ex 14 Ex 15 Ex 7 (Control) (Comparative) Automotive spring sections 21 3 5 4 7 12100 Cycles GMW14872mm Average Scribe Creep(rubber-containing topcoat)Automotive spring sections 24 5 6 5 9 16100 Cycles GMW14872mm Average Scribe Creep(non-rubber containingtopcoat)

[0084] As shown in Table 6, when the Control Example 11 , a composition containing 47.8% zinc and representative of the compositions of WO 2023 / 215677 A1 , was modified with 10% conductive rubber particles in Example 12 improved corrosion is demonstrated. Improved corrosion performance is also observed with Example 13, which is like Example 12, but including the use of 5% magnesium oxide. Example 14 utilizes low molecular weight epoxy resin and micronized rubber exhibiting improved corrosion resistance. Example 15 is identical to Example 14 but utilizes a different grade of zinc flake, and exhibits improved corrosion resistance compared to the Control. Examples 12, 13, 14 and 15 all exhibit improved corrosion performance over the comparative epoxy primercomposition containing 80% zinc (Example 7). A commercial automotive spring topcoat, PCM90195 available from PPG was utilized for this corrosion testing. This topcoat contains conductive rubber particles for impact resistance.

[0085] Again, an additional epoxy topcoat was included in the testing reported in Table 6: PCM90200 available from PPG, a commercially available epoxy topcoat which does not contain micronized rubber. Corrosion testing, in conjunction with testing with PCM90195 was conducted to determine if the use of micronized, conductive rubber particles in the topcoat contributed to the performance of the primer topcoat coating system. All Examples 11 , 12, 13, 14, 15 and 7 exhibited weaker corrosion performance when a topcoat not containing rubber particles was utilized, demonstrating the enhanced performance of the total system when micronized, conductive rubber particles are contained in the topcoat applied over the primer composition.Zinc rich compositions with micronized rubber containing primer compositions at zinc levels down of 27.8% zincPreparation of compositions

[0086] Each of the components listed in Table 7 was weighed in a container and mixed in a prism high speed mixer for 15 seconds at 2500 RPM to form a dry homogeneous mixture. The mixture was then melt mixed in a Werner Pfleiderer 19mm twin screw extruder with an aggressive screw configuration and a speed of 500 RPM. The first zone was set at 50°C, and the second, third, and fourth zones were set at 95°C. The feed rate was such that a torque of 40%-50% was obtained on the equipment and maintained for all examples. The extruded material dropped onto a set of chill rolls to cool and re-solidify the mixtures into solid chips. Aluminum oxide was incorporated with the cooled chips. The chips were milled to a fine powder in a Mikro ACM®-1 Air Classifying Mill to obtain a fine powder that was tap-sieved with a 100-mesh screen to achieve final particle size ranges between 5 to 149 microns with a majority of the particles from 35 to 45 microns. The resulting coating compositions for each of Examples 16 and 17 were solid particulate powder coating compositions that were free flowing.Table 7Ingredient Ex 16 Ex 17(Control)Epon 2004 40.24 34.56NPES-903 5.01 4.30Epon 1001 F 11.10 9.53Epikure P-202 14.50 12.46Imidazole150.10 0.10PL-200A 0.30 0.30Benzoin 0.50 0.50MicroDyne 50 - 10.00Magchem - - Tuball Matrix Beta 809 0.20 0.20#2 ZINC 13.5 13.50DUST / 330LL10ProFlake Zn 2000 14.3 14.30Aluminum Oxide 0.25 0.25Total Grams 100.00 100.00152-METHYL-1 H-IMIDAZOLE from Cabot Corporation

[0087] The Example powder coating composition in Table 7 and control were applied with an Encore Nordson powder coating cup gun at 75kV, 15mA, 10 psi atomizing and 10 psi conveying flow air over automotive spring sections, approximately 7-8 inches in length that were obtained from a spring supplier with pretreatment applied by the customer. For application the spring sections were heated to 375°F and the primer compositions were applied to a coating thickness between 38um to 45um.

[0088] A commercial topcoat, PCM90195 available from PPG, was immediately applied over the coatings with the same settings to a film build of 255um to 51 Oum. The spring sections were then baked 2O’@375°F to cure the coating layers.

[0089] In preparation of corrosion testing, the spring sections were scribed utilizing a Dremel tool with a cutting disc attachment cutting through the coating layers down to the metal approximately 5 inches in length of the 7-8 inch long spring sections. After testing, the spring sections were scraped free of lose coating and corrosion products under a warm water flow with a knife, lifting up and removing any loose coating. The exposed metal and corrosion product, calledscribe creep, was measured as total scribe creep across the exposed area 90° to the scribe line. 3 spring sections were measured in ten locations, and the average of 30 readings is reported below in mm total scribe creep.

[0090] Comparative corrosion was done as per GMW14872 cyclic corrosion for 100 cycles. For corrosion testing the panels were cut through to the metal with a carbine tipped pen to the metal substrate down the middle of the test panels approximately 4 inches on a 6- inch test panel. After testing, the panels were scraped free of lose coating and corrosion products under a warm water flow exposing the area that experienced coating failure. The exposed cleaned area, called scribe creep, was measured as total scribe creep across the exposed area 90° to the scribe line. An average of 10 readings on two panels is reported in millimeters total scribe creep in the Table 8.Table 8Ex 16 Ex17(Control)Automotive spring sections 16 3100 Cycles GMW14872 mmAverage Scribe Creep

[0091] As shown in corrosion testing when the control, Example 16, a composition containing 27.8% zinc is modified with 10% micronized rubber in Example 17. The modified rubber formulation exhibits improved corrosion over the non-rubber modified comparable.Zinc rich Hybrid primer compositions with micronized rubber at zinc levels down to 37.8% to 47.8% zincMaking of compositions

[0092] Each of the components listed in Table 9 was weighed in a container and mixed in a prism high speed mixer for 15 seconds at 2500 RPM to form a dry homogeneous mixture. The mixture was then melt mixed in a Werner Pfleiderer 19mm twin screw extruder with an aggressive screw configuration and a speed of 500 RPM. The first zone was set at 50°C, and the second, third, and fourth zones were set at 95°C. The feed rate was such that a torque of 40%-50% was obtained on the equipment and maintained for all examples. The extruded material dropped onto a set of chill rolls to cool and re-solidify the mixtures into solid chips.Aluminum oxide was incorporated with the cooled chips. The chips were milled to a fine powder in a Mikro ACM®-1 Air Classifying Mill to obtain a fine powder that was tap-sieved with a 100-mesh screen to achieve final particle size ranges between 5 to 149 microns with a majority of the particles from 35 to 45 microns. The resulting coating compositions for each of Examples 18 through 21 were solid particulate powder coating compositions that were free flowing.Tab e9Ingredient Ex 18 Ex 19 Ex 20 Ex 21(comparative) (comparative)Pioester 72241625.87 30.95 20.79 25.87 NPES-903 25.08 30.00 20.16 25.08 PL-200A 0.30 0.30 0.30 0.30 Benzoin 0.50 0.50 0.50 0.50 MicroDyne 50 - - 10.00 10.00 Tuball Matrix 0.20 0.20 0.20 0.20 Beta 809#2 ZINC 33.5 23.50 33.5 23.50 DUST / 330LL10ProFlake Zn 14.3 14.30 14.3 14.30 2000Aluminum Oxide 0.25 0.25 0.25 0.25Total Grams 100.00 100.00 100.00 100.00 Acid functional resin available from Panolam IndustriesApplication and testing

[0093] The Example powder coating compositions in Table 9 were applied as primers with an Encore Nordson powder coating cup gun at 75kV, 15mA, 10 psi atomizing and 10 psi conveying flow air. The coating thickness was 38 microns to 51 microns over CRS 0700 C59 test panels available from ACT Test Panels, LLC. The coatings were gelled at 375°F for 5 minutes to form a primer coating layer and allowed to cool. A commercial topcoat available from PPG, PCTZ39104, was applied over the primer compositions with an Encore Nordson powder coating cup gun at 75kV, 15mA, 10 psi atomizing and 10 psi conveying flow air. The topcoat coating thickness was 51 urn to 70um. Both primer and topcoat were cured with a 2O’@ 375°F bake.

[0094] Comparative corrosion testing was done as per GMW14872 Cyclic Corrosion Laboratory Test for 100 cycles. For corrosion testing the panels werecut through to the metal with a carbine tipped pen to the metal substrate down the middle of the test panels approximately 4 inches on a 6-inch test panel. After testing, the panels were scraped free of loose coating and corrosion products under a warm water flow exposing the area that experienced coating failure. The exposed cleaned area, called scribe creep, was measured as total scribe creep across the exposed area 90° to the scribe line. An average of 10 readings on two panels is reported in millimeters total scribe creep in Table 10.Table 10Ex 18 Ex 19 Ex 20 Ex 21 (Control) (Control)CRS C700 C59 panels, 100 Cycles 11 11 6 7 GMW14872 Average mmAverage Scribe Creep

[0095] As shown in the comparative hybrid Examples 18 and 19 with 48% and 38% total zinc loading, when modified with micronized rubber as in Examples 20 and 21 , corrosion performance is improved with the rubber modification.Zinc rich polyester primer compositions with micronized rubber at zinc levels down to 37.8% to 47.8% zincMaking of compositions

[0096] Each of the components listed in Table 11 was weighed in a container and mixed in a prism high speed mixer for 15 seconds at 2500 RPM to form a dry homogeneous mixture. The mixture was then melt mixed in a Werner Pfleiderer 19mm twin screw extruder with an aggressive screw configuration and a speed of 500 RPM. The first zone was set at 50°C, and the second, third, and fourth zones were set at 110°C. The feed rate was such that a torque of 40%-50% was obtained on the equipment and maintained for all examples. The extruded material dropped onto a set of chill rolls to cool and re-solidify the mixtures into solid chips. Aluminum oxide was incorporated with the cooled chips. The chips were milled to a fine powder in a Mikro ACMO-1 Air Classifying Mill to obtain a fine powder that was tap-sieved with a 100-mesh screen to achieve final particle size ranges between 5 to 149 microns with a majority of the particles from 35 to 45 microns. The resulting coating compositions for each of Examples 22 through26 were solid particulate powder coating compositions that were free flowing. Note Examples 22 and 23 are comparative.Ta ble 11Ingredient Ex 22 Ex 23 Ex 24 Ex 25 Ex 26 (comp) (comp)Uralac P34801748.56 58.22 43.72 38.89 48.56 Primid 552181.70 2.03 1.53 1.36 1.70 PL-200A 0.90 0.90 0.90 0.90 0.90 Benzoin 0.50 0.50 0.50 0.50 0.50 MicroDyne 50 - - 5.0 10.0 10.0 Tubal I Matrix Beta 0.20 0.20 0.20 0.20 0.2 809#2 ZINC 33.5 23.50 33.5 33.50 23.5 DUST / 330LL10ProFlake Zn 2000 14.3 14.30 14.3 14.30 14.30 Aluminum Oxide 0.25 0.25 0.25 0.25 0.25Total Grams 100.00 100.00 100.00 100.00 100.00 Acid functional resin available from Covestro AGHydroxyalkylamide crosslinker available from EMS-Chemie Holding AGApplication and testing

[0097] The Example powder coating compositions in Table 11 were applied with an Encore Nordson powder coating cup gun at 75kV, 15mA, 10 psi atomizing and 10 psi conveying flow air. The coating thickness was 38 microns to 51 microns over CRS C700 C59 test panels available from ACT Test Panels, LLC. The coatings were gelled at 375°F for 5 minutes to form a primer coating layer and allowed to cool. A commercial topcoat available from PPG, PCTZ39104, was applied over the primer compositions with an Encore Nordson powder coating cup gun at 75kV, 15mA, 10 psi atomizing and 10 psi conveying flow air. The topcoat coating thickness was 51 urn to 70um. Both primer and topcoat were cured with a 2O’@ 375°F bake.

[0098] Comparative corrosion testing was done as per GMW14872 Cyclic Corrosion Laboratory Test for 40 cycles. For corrosion testing the panels were cut through to the metal with a carbine tipped pen to the metal substrate down the middle of the test panels approximately 4 inches on a 6-inch test panel. After testing, the panels were scraped free of loose coating and corrosion productsunder a warm water flow exposing the area that experienced coating failure. The exposed cleaned area, called scribe creep, was measured as total scribe creep across the exposed area 90° to the scribe line. An average of 10 readings on two panels is reported in millimeters total scribe creep in Table 12.Table 12Ex 22 Ex 23 Ex 24 Ex 25 Ex 26 (Control) (Control)CRS C700 C59 panels, 40 4 5 3 3 3 Cycles GMW14872 AverageScribe Creep, mm

[0099] As shown in the Control Examples 22 and 23, with 48 and 38% total zinc loading, when modified with micronized rubber as in Examples 24, 25, and 26 improved corrosion performance is demonstrated.

[0100] Whereas particular examples of this disclosure have been described above for purposes of illustration, it will be evident to those skilled in the art that numerous variations of the details of the present disclosure may be made without departing therefrom as defined in the appended claims. Although various examples of the disclosure have been described in terms of "comprising", embodiments consisting essentially of or consisting of are also within the scope of the present disclosure.

Claims

1. What is claimed is:2.1 . A powder coating composition comprising:3.a) zinc metal in an amount of at least 20 percent by weight and less than 50 percent by weight, based on total weight of the powder coating composition; b) a resinous binder component in an amount from 35 percent by weight to 77 percent by weight, based on total weight of the powder coating composition; and c) micronized rubber particles in an amount from 3 percent by weight to 15 percent by weight, based on total weight of the powder coating composition; wherein the micronized rubber particles demonstrate a particle size smaller than ASTM E11 Test Sieve Size 200 mesh (74 microns), as determined using ASTM test method D-5644-18.

2. The powder coating composition of claim 1 , wherein the zinc metal comprises zinc flakes and / or zinc particles.

3. The powder coating composition of claim 1 or 2, wherein the zinc metal is present in an amount of at least 20 percent by weight and less than 40 percent by weight, based on total weight of the powder coating composition.

4. The powder coating composition of any of claims 1 to 3, wherein the zinc metal is present in at least two physical forms including zinc flakes, at a weight ratio of zinc flakes to zinc in other physical forms of 1 :4 to 4:1.

5. The powder coating composition of claim 4, wherein the zinc flakes are present in an amount from 10 percent by weight to 20 percent by weight, based on total weight of the powder coating composition.

6. The powder coating composition of claim 1 , wherein the powder coating composition does not contain zinc flakes.

7. The powder coating composition of any preceding claim, wherein the resinous binder component comprises a film-forming resin comprising an epoxy resin and / or a polyester resin.

8. The powder coating composition of claim 7, wherein the film-forming resin comprises the epoxy resin, and wherein the epoxy resin demonstrates a weight average molecular weight of 500 to 1000 Da, determined by gel permeation chromatography using a polystyrene standard, and an epoxy equivalent weight of 450 to 550 g / equivalent, and is present in the powder coating composition in an amount of 5 to 15 percent by weight, based on total weight of the powder coating composition.

9. The powder coating composition claim 7, wherein the film-forming resin comprises the epoxy resin, and wherein the epoxy resin demonstrates (i) a weight average molecular weight of 500 to 11000 Da, determined by gel permeation chromatography using a polystyrene standard, and / or (ii) an epoxy equivalent weight of 450 to 5100 g / equivalent.

10. The powder coating composition of any of claims 7 to 9, wherein the filmforming resin comprises the epoxy resin and the polyester resin.

11. The powder coating composition of any preceding claim, wherein the resinous binder component further comprises a crosslinking agent selected from phenolic resins, amino resins, epoxy functional compounds, isocyanurates, beta-hydroxy (alkyl) amides, alkylated carbamates, (meth)acrylates, isocyanates, blocked isocyanates, polyacids, anhydrides, organometallic acid-functional materials, polyamines, polyamides, aminoplasts, carbodiimides, oxazolines, tetrakis(methoxymethyl)glycoluril, hydroxyalkyl urea, and combinations thereof.

12. The powder coating composition of any preceding claim, wherein the composition further comprises carbon nanotubes in an amount from 0.001 percent by weight to 5 percent by weight based on total weight of the powder coating composition.

13. The powder coating composition of any preceding claim, wherein the composition further comprises magnesium oxide particles in an amount of 2 to 15 percent by weight, based on total weight of the powder coating composition.

14. The powder coating composition of any preceding claim, wherein the micronized rubber particles are prepared from used rubber tires.

15. A coated article comprising:16.a) a substrate; and17.b) a coating layer formed from the powder coating composition according to any one of claims 1 to 14 applied to at least a portion of the substrate.

16. The coated article of claim 15, wherein the substrate comprises steel.

17. The coated article of claim 15 or 16, wherein the substrate comprises a vehicle suspension spring.

18. The coated article of any of claims 15 to 17, further comprising an additional coating composition applied to at least a portion of the powder coating composition.

19. The coated article of claim 18, wherein the additional coating composition comprises micronized rubber particles.

20. The coated article of any of claims 18 to 19, wherein after application of the powder coating composition and the additional coating composition to the substrate and after curing the coating compositions, the coated article demonstrates improved corrosion resistance when subjected to GMW14872 Cyclic Corrosion Laboratory Test for 100 cycles, compared to an analogous coated article wherein the additional coating composition does not comprise rubber particles.

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