WO2024163416A1 - Elastomeric erosion coating system - Google Patents

Abstract

Coating systems with better erosion resistance than steel on exposure to silica or sand are described herein. The systems include a thermoset resin as a basecoat with a thermoplastic topcoat applied over the basecoat. Optionally, a liquid primer may be applied to the substrate prior to the application of the basecoat. Methods of making and using the coating systems are also described herein.

Description

EEASTOMERIC EROSION COATING SYSTEM

BACKGROUND OF THE INVENTION

[001] Components utilized in oil field operations, such as the pipeline used in fracking wells, for example, are often exposed to harsh environments. These components are exposed to high flow rates, high pressures, and other environmental conditions. Crude oil contains corrosive ingredients such as carbon dioxide (CO2), hydrogen sulfide (H2S), organic acids, dissolved gases, and salt water. Oil sand comprises CO2 and corrosive ions such as chloride (Cl’), bicarbonate (HCO3 ), and sulfate (SO4²’). In some extraction regimes, sand can be mixed with the flowing fluid to form multiphase solid-liquid mixtures. Flowing mixtures in piping and components, such as elbows, and pump impellers, may lead to solid particle erosion together with corrosion. Erosion and corrosion can reduce the equipment's lifetime due to a higher rate of material loss, resulting in replacement and downtime.

[002] Standard fusion-bonded epoxy (FBE) powder coatings are frequently used to coat and protect surfaces and components in the oil and gas industry and are known to provide effective corrosion resistances. These coatings are sometimes used as erosion-resistant coatings as well. However, these FBE coatings have been known to erode from pipe elbows within three months of exposure, followed by pipe failure within six months due to solids and corrosive material flowing through these components at high pressure and temperature. The combination of erosion and erosion/corrosion significantly reduces the lifetime of equipment used in the industry and leads to high rates of material loss and high costs associated with repair and shutdown of production.

[003] From the foregoing, it will be appreciated that what is needed in the art is a coating system for use in the oil and gas industry that will be resistant to both corrosion and erosion. Such coating systems and methods for preparing and using the same are disclosed and claimed herein.

SUMMARY

[004] The present invention provides an erosion-resistant coating system. In an embodiment, the coating system includes a first coating applied to a substrate and a second coating applied over the first coating, the second coating comprising a thermoplastic component, wherein the coating system is erosion resistant.

[005] In another embodiment, the present description provides a method of coating a substrate. The method includes the steps of providing a substrate, contacting at least one surface of the substrate with an erosion-resistant coating system, and then subjecting the substrate with the coating system applied thereon to conditions effective to form a cured coating on the substrate. The erosion-resistant coating system includes a first coating applied to a substrate and a second coating applied over the first coating, the second coating comprising a thermoplastic component.

[006] In yet another embodiment, the present description provides a coated article. The article includes a substrate with an erosion-resistant coating system applied thereon. The erosion-resistant coating system includes a first coating applied to a substrate and a second coating applied over the first coating, the second coating comprising a thermoplastic component.

[007] The above summary of the present invention is not intended to describe each disclosed embodiment or every implementation of the present invention. The description that follows more particularly exemplifies illustrative embodiments. In several places throughout the application, guidance is provided through lists of examples, which can be used in various combinations. In each instance, the recited list serves only as a representative group and should not be interpreted as an exclusive list.

[008] The details of one or more embodiments of the invention are set for in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[009] Fig. 1 depicts a microscope image of the top view of a coated erosion panel. [0010] Fig. 2 depicts a microscope image of the side view of a coated erosion panel. [0011] Fig. 3 shows profilometry and depth measurement of a coated erosion panel.

[0012] Fig. 4 is a graphical representation of the rate of erosion of a coating relative to bare steel.

[0013] Fig. 5 is a graphical representation of the average erosion rate of coatings relative to steel. [0014] Fig. 6 is a graphical representation of the storage modulus (E’) following immersion testing.

[0015] Fig. 7 is a graphical representation of the storage modulus (E’) as a function of temperature.

[0016] Fig. 8 is a graphical representation of the E”/E’ ratio (tan 5).

[0017] Fig. 9 is a graphical representation of coating hardness of multiple coatings.

SELECTED DEFINITIONS

[0018] Unless otherwise specified, the following terms as used herein have the meanings as provided below.

[0019] The term “component” refers to any compound that includes a particular feature or structure. Examples of components include compounds, monomers, oligomers, polymers, and organic groups contained there.

[0020] The term “substantially free” of a particular compound or component means that the compositions described herein contain less than 5% by weight of the component, based on the total weight of the composition. The term “essentially free” of a particular compound or component means that the compositions described contain less than 2% by weight of the component, based on the total weight of the composition. The term “completely free” of a particular component means that the compositions described herein contain less than 1% by weight, based on the total weight of the composition.

[0021] The term “crosslinker” refers to a molecule capable of forming a covalent linkage between polymers or between two different regions of the same polymer.

[0022] The term “particle size” as used herein refers to particle size distribution, i.e., the frequency of particles of a certain size in a sample of a component (such as a powder, granulate, or suspension) of the compositions described herein. The particle size may be described as D50 (the mean or average particle size), D90 (the particle size diameter where ninety percent of the distribution has a smaller particle size and ten percent has a larger particle size), or D10 (the particle size diameter where ten percent of the distribution has a smaller particle size and ninety percent has a larger particle size). Particle size may be determined or analyzed by various methods known to those of skill in the art, including Laser Diffraction (LD), Dynamic Light Scattering (DLS), Dynamic Image Analysis (DIA) or Sieve Analysis. Unless otherwise indicated, particle size as described herein is determined by dynamic light scattering or otherwise provided by the manufacturer of a particular component. [0023] As used herein, the term “erosion” refers to the damage to a material caused by mechanical movement or impact between particles and a surface. Specifically, as defined by NACE International, “erosion” means “ [t]he progressive loss of material from a solid surface resulting from mechanical interaction between that surface and a fluid, a multicomponent fluid, or solid particles carried with the fluid. These particles may be present in a liquid, a slurry, or as particles suspended in a liquid or slurry, for example. The impact of these particles at high velocity against a surface results in removal of material from the surface. This is in contrast to “abrasion,” a term that refers to the damage to a material caused by friction when one material rubs against another, and material is scraped away from the surface. Accordingly, an “erosion-resistant” coating or coating system is one that resists erosion damage or coating loss as a result of erosion, and the property of erosion resistance can be demonstrated or measured by standard methods described herein.

[0024] 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.

[0025] 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 appreciable chemical change. In contrast, a “thermoset” refers to a material that is crosslinked and does not “melt.” [0026] Unless otherwise indicated, a reference to a “(meth)acrylate” compound (where “meth” is bracketed) is meant to include both acrylate and methacrylate compounds.

[0027] 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.

[0028] Unless otherwise indicated, the term “polymer” includes both homopolymers and copolymers (i.e., polymers of two or more different monomers).

[0029] The term “comprises” and variations thereof do not have a limiting meaning where these terms appear in the description and claims.

[0030] The terms “preferred” and “preferably” refer to embodiments of the invention 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 or more preferred embodiments does not imply that other embodiments are not useful and is not intended to exclude other embodiments from the scope of the invention.

[0031] As used herein, “a,” “an,” “the,” “at least one,” and “one or more” are used interchangeably. Thus, for example, a coating composition that comprises “an” additive can be interpreted to mean that the coating composition includes “one or more” additives.

[0032] Also herein, the recitations of numerical ranges by endpoints include all numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.). Furthermore, disclosure of a range includes disclosure of all subranges included within the broader range (e.g., 1 to 5 discloses 1 to 4, 1.5 to 4.5, 1 to 2, etc.).

DETAILED DESCRIPTION

[0033] The present description provides an erosion-resistant coating system. The coating system includes a first coating applied to a substrate and at least a second coating applied over the first coating, where the second coating is a thermoplastic component. Erosionresistant coating systems of the type described herein demonstrate erosion performance similar to steel when exposed to particular matter, including sand, for example. These coating systems also have excellent adhesion and appearance, and do not blister or swell when exposed to corrosive environments.

[0034] In some embodiments, the present description provides an erosion-resistant coating system that includes a first coating applied to a substrate. In an aspect, the first coating is applied to a substrate, optionally to a substrate with a primer coating applied thereon. In a preferred aspect, the first coating is corrosion resistant. In an aspect, the first coating is thermoplastic. In another aspect, the first coating is a thermoset. In an aspect, the first coating may be a one-component coating. In another aspect, the first coating may be a two- component coating. In yet another aspect, the first coating may be a liquid coating and in even another aspect, the first coating may be a powder coating.

[0035] The first coating is derived from a coating composition that includes at least one binder resin component. In an aspect, the binder resin component is selected from epoxy, polyester, polyurethane, polyamide, acrylic, polyvinylchloride, nylon, fluoropolymer, silicone, other resins, or combinations thereof.

[0036] In a preferred aspect, the binder resin component is an epoxy or polyepoxide binder resin component. Suitable epoxy resin components or polyepoxides preferably include at least two 1,2-epoxide groups per molecule. In an aspect, the epoxy equivalent weight is preferably from about 100 to about 4000, more preferably from about 500 to 1000, based on the total solids content of the polyepoxide. The polyepoxides may be aliphatic, alicyclic, aromatic, or heterocyclic. In an aspect, the polyepoxides may include substituents such as, for example, halogen, hydroxyl group, ether groups, and the like.

[0037] Suitable epoxy resin compositions or polyepoxides used in the composition and method described herein include without limitation, epoxy ethers formed by reaction of an epihalohydrin, such as epichlorohydrin, for example, with a polyphenol, typically and preferably in the presence of an alkali. Suitable polyphenols include, for example, catechol, hydroquinone, resorcinol, bis(4-hydroxyphenyl)-2,2-propane (Bisphenol A), bis(4- hydroxyphenyl)- 1,1 -isobutane, bis (4-hydroxyphenyl)- 1,1 -ethane, bis (2-hydroxyphenyl)- methane, 4,4-dihydroxybenzophenone, 1, 5-hydroxynaphthalene, and the like. Bisphenol A and the diglycidyl ether of Bisphenol A are preferred.

[0038] Suitable epoxy resin compositions or polyepoxides may also include polyglicydyl ethers of polyhydric alcohols. These compounds may be derived from polyhydric alcohols such as, for example, ethylene glycol, propylene glycol, butylene glycol, 1,6-hexylene glycol, neopentyl glycol, diethylene glycol, glycerol, trimethylol propane, pentaerythritol, and the like. Other suitable epoxides or polyepoxides include polyglycidyl esters of polycarboxylic acids formed by reaction of epihalohydrin or other epoxy compositions with aliphatic or aromatic polycarboxylic acid such as, for example, succinic acid, adipic acid, azelaic acid, sebacic acid, maleic acid, fumaric acid, phthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, trimellitic acid, and the like. In an aspect, dimerized unsaturated fatty acids and polymeric polycarboxylic acids can also be reacted to produce polyglycidyl esters of polycarboxylic acids.

[0039] In an embodiment, the epoxy resin compositions or polyepoxides described herein are derived by oxidation of an ethylenically unsaturated alicyclic compound. Ethylenically unsaturated alicylic compounds may be epoxidized by reaction with oxygen, perbenzoic acid, acid-aldehyde monoperacetate, peracetic acid, and the like. Polyepoxides produced by such reaction are known to those of skill in the art and include, without limitation, epoxy alicylic ethers and esters.

[0040] In an embodiment, the epoxy resin compositions or polyepoxides described herein include epoxy novolac resins, obtained by reaction of epihalohydrin with the condensation product of aldehyde and monohydric or polyhydric phenols. Examples include, without limitation, the reaction product of epichlorohydrin with condensation product of formaldehyde and various phenols, such as for example, phenol, cresol, xylenol, butylmethyl phenol, phenyl phenol, biphenol, naphthol, bisphenol A, bisphenol F, and the like.

[0041] In an embodiment, the first coating composition described herein is a powder coating composition. Thermoset materials are generally preferred for use as polymeric binders in powder coating applications. The powder composition described herein is a curable composition that includes at least one curing agent. In an embodiment, the curing agent described herein helps achieve a solid, flexible, epoxy-functional powder composition.

Suitable curing agents include, for example, epoxide-functional compounds (e.g., triglycidyl- isocyanurate), hydroxyalkyl amides (e.g., beta-hydroxyalkyl amide, commercially known as PRIMID), blocked isocyanates or uretdiones, amines (e.g., dicyandiamide), dihydrazides (e.g., adipic acid dihydrazide (ADH), isophthalic dihydrazide (IDH), sebacic dihydrazide (SDH), and the like), phenolic-functional resins, carboxyl-functional curatives, and the like. The curing reaction may be induced thermally, or by exposure to radiation (e.g., UV, UV-vis, visible light, IR, near-IR, and e-beam).

[0042] In an aspect, the curing agent is selected to be compatible with the epoxy resin composition and operate to cure the powder composition at the temperature used to cure and apply the powder composition. Therefore, for the powder composition described herein, the curing agent is preferably selected to have a melting or softening point within the range of application temperature described herein, i.e., preferably about 150° C. to 300° C., more preferably about 220° C. to 260° C.

[0043] Accordingly, in a preferred embodiment, the powder composition described herein is a fusion-bonded epoxy (FBE) composition. Preferred compositions include an epoxy resin prepared from a homogenous mixture of polyglycidyl ether of a polyhydric phenol, along with a dihydrazide or dicyandiamide curing agent. In an aspect, the fusion-bonded epoxy composition is present in an amount of about 20 to 90 wt %, preferably about 30 to 80 wt %, more preferably about 40 to 70 wt %, and most preferably about 50 to 60 wt %, based on the total weight of the powder composition. Examples of suitable commercially available FBE compositions include the PIPECLAD line of products (Sherwin-Williams), the CORVEL line of products (Akzo Nobel), and the like.

[0044] Suitable FBE powder compositions as used herein include compositions with particle size of about 5 to 20 pm, preferably 10 to 15 pm (D10), about 40 to 70 pm, preferably 50 to 60 pm (D50), and about 100 to 140 pm, preferably 110 to 130 pm (D90), as measured by dynamic light scattering analysis. [0045] The first coating of the system as described herein is a cured film derived from an FBE powder composition. Suitable FBE powder compositions as used herein include compositions with high porosity resistance. Without limiting to theory, it is believed that higher porosity resistance provides better corrosion protection by minimizing the penetration of moisture into the substrate. Therefore, a high porosity resistance coating or film is one that has minimal voids, or pores, on the film surface, i.e., the film has low porosity. The porosity of the film is determined and rated by methods known to those of skill in the art, including preferably by the method described in the standard CSA Z245.20 series (Plant-applied External Coatings for Steel Pipe). Accordingly, in an embodiment, the first coating of the system described herein is a cured film with porosity rating of about 1 to 4, preferably 1 to 2, as determined by CSA Z245.20, wherein a rating of 1 indicates the lowest porosity and a rating of 5 the highest porosity.

[0046] The first coating of the system described herein is a corrosion-resistant coating. The corrosion resistance of the coating described herein may be determined by standard methods known to those of skill in the art, including by measuring cathodic disbondment according to the methods described in CSA Z245.20 (Plant- Applied External Coatings for Steel Pipe). A coating is considered to have optimal corrosion resistance if it demonstrates a coating loss of less than 15 mm after 28-day exposure at 65°C.

[0047] Without limiting to theory, the corrosion resistance of the first coating, preferably a FBE powder coating, is partially dependent on the application temperature. At the appropriate application temperature, a spray applied FBE powder coating will melt and flow into the blast profile of the substrate and then cure to form a durable coating with minimal porosity and optimal corrosion resistance. At too high an application temperature, pores, or voids where the film is not continuous, are more likely to occur, which makes the substrate more permeable to water and could lead to corrosion of the substrate. At too low an application temperature, on the other hand, the sprayed FBE powder may not melt sufficiently, which reduces its adhesion. By fine-tuning application temperatures, it is possible to reduce the porosity of applied FBE coatings and obtain a coating with optimal corrosion resistance. [0048] Accordingly, in an embodiment, the first coating of the erosion-resistant system described herein is applied to a substrate at a temperature of about 300F to 375F (approximately 149°C to 191°C), preferably 325F to 350F (approximately 163°C to 177°C). In an aspect, the substrate is heated to the desired temperature and the first coating is then applied to the heated substrate to allow the composition to melt, flow, and level out over the surface of the substrate. [0049] As described herein, the first coating may be applied at a dry film thickness (DFT) appropriate for the anticipated end use of the substrate. Accordingly, in an embodiment, the first coating is applied at DFT of about 6 to 20 mil (approximately 152 pm to 508 pm), preferably about 8 to 16 mil (approximately 203 pm to 406 pm), more preferably about 10 to 14 mil (approximately 254 pm to 356 pm).

[0050] In some embodiments, the first coating of the erosion-resistant system described herein is applied over a primer that is in contact with and/or directly bonded to the unprimed, pretreated, or clean-blasted substrate surface. The primer is intended to be a corrosionresistant coating applied to the metal, and the first coating of the erosion-resistant system described herein is then a basecoat applied over the primer layer. The primer may be a powder coating or a liquid coating. The primer coating or layer is optional, however, and the first coating or basecoat may be applied directly to the unprimed, pretreated, or clean-blasted substrate surface even without a primer coating. When used, the primer layer may comprise a phenolic primer such as a phenol-formaldehyde resin or an epoxy-phenolic resin, for example.

[0051] In some embodiments, the present description provides an erosion-resistant coating system that includes a second coating applied to a substrate. In an aspect, the second coating is applied to a substrate with a first coating applied thereon. In another aspect, the second is applied directly to the substrate without a first coating applied thereon. In a preferred aspect, the second coating is an erosion-resistant coating. In an aspect, the second coating is thermoplastic. In another aspect, the second coating is a thermoset. In an aspect, the second coating may be a one-component coating. In another aspect, the second coating may be a two-component coating. In yet another aspect, the second coating may be a liquid coating and in even another aspect, the second coating may be a powder coating.

[0052] In a preferred embodiment, the erosion-resistant second coating is a thermoplastic coating, preferably a powder coating composition that includes at least one binder resin component. In an aspect, the binder resin component is a polyolefin selected from polyethylene, polypropylene, and the like, and mixtures or combinations thereof.

[0053] In a preferred aspect, the polyolefin is a modified component, preferably an acid- modified component, obtained by combining a polyolefin with at least one a,P-unsaturated carboxylic acid or acid anhydride thereof, such as, for example, maleic acid, itaconic acid, citraconic acid, acid anhydride thereof, or mixtures or combinations thereof. Of these, acid anhydride forms are generally preferred, and maleic acid anhydride is more preferred. Suitable examples of modified polyolefins as described herein include, without limitation, maleic acid anhydride-modified polypropylene, maleic acid anhydride-modified propyleneethylene copolymers, maleic acid anhydride-modified propylene-butene copolymers, maleic acid anhydride-modified propylene-ethylene-butene copolymers, and the like. These acid- modified polyolefins can be used singly or as mixtures or combinations of two or more modified polyolefins.

[0054] In a preferred embodiment, the second coating is derived from maleic anhydride- modified polypropylene (PP-MA). Crystalline or semi-crystalline forms of PP-MA are particularly preferred, as they demonstrate better adhesion to a substrate surface, and accordingly form a more effective erosion-resistant coating, as well as providing effective corrosion resistance and barrier properties. In an aspect, the crystalline PP-MA described herein has molecular weight (Mw, weight average molecular weight) of 40,000 to 180,000, more preferably 50,000 to 160,000, even more preferably 60,000 to 150,000, particularly preferably 70,000 to 140,000, and most preferably 80,000 to 130,000.

[0055] In an embodiment, the second coating is an erosion-resistant powder coating derived from a binder resin component comprising a modified polyolefin, preferably maleic anhydride-modified polypropylene (PP-MA). The second coating as described herein may be a single layer or multi-layer extruded thermoplastic film.

[0056] The second coating as described herein is an erosion-resistant powder coating. Without limiting to theory, it is believed that the particle size (D90) of the second coating is critical to effective erosion resistant performance. By maintaining the D90 particle size below about 300 pm, it is possible to limit or reduce the porosity of the erosion-resistant coating. A porous coating is one that has significant voids or gaps in the coating, and such coatings are more susceptible to erosion and failure when in contact with large particulate matter such as the sand or grit encountered during oil and gas drilling operations, for example.

[0057] Accordingly, in an embodiment, suitable extruded films derived from maleic anhydride-modified polypropylene (PP-MA) have particle size of about 60 to 100 pm, preferably 70 to 90 pm (D10), about 220 to 260 pm, preferably 230 to 250 pm (D50), and about 370 to 420 pm, preferably 390 to 410 pm (D90), as measured by dynamic light scattering analysis and as provided by the manufacturer.

[0058] In another aspect, the extruded films for the second coating described herein are derived from maleic anhydride-modified polypropylene sieved through an 84T mesh and having particle size of about 40 to 90 pm, preferably 50 to 70 pm (D10), about 120 to 160 pm, preferably 130 to 150 pm (D50), and about 220 to 260 pm, preferably 230 to 250 pm (D90), as measured by as determined by sieve analysis according to ASTM D1921-18. [0059] Without limiting to theory, it is believed that higher porosity resistance provides better erosion resistance by minimizing areas where contact with large particulate matter could cause erosion or coating loss. Therefore, a high porosity resistance coating or film is one that has minimal voids, or pores, on the film surface, i.e., the film has low porosity. The porosity of the film is determined and rated by methods known to those of skill in the art, including preferably by the method described in the standard CSA Z245.20 series (Plant- applied External Coatings for Steel Pipe). Accordingly, in an embodiment, the second coating of the system described herein is a cured film with porosity rating of about 1 to 4, preferably 1 to 2, as determined by CSA Z245.20, wherein a rating of 1 indicates the lowest porosity and a rating of 5 the highest porosity.

[0060] As described herein, the second coating may be applied at a dry film thickness (DFT) appropriate for the anticipated end use of the substrate, i.e., specifically as an erosionresistant coating. Accordingly, in an embodiment, the second coating is applied at DFT of about 20 to 100 mil (approximately 508 pm to 2540 pm), preferably about 30 to 85 mil (approximately 762 pm to 1651 pm), and more preferably about 40 to 60 mil (approximately 1016 pm to 1524 pm).

[0061] In an embodiment, the first and second coatings as described herein combine to form the erosion-resistant coating system of the invention. In an aspect, the second coating is applied over the first coating to form a molecular composite. As used herein, the term “molecular composite” refers to a system where two or more coatings are chemically bonded or crosslinked at the interface between the coatings such that interlayer adhesion is maximized. This molecular composite forms the erosion-resistant coating system described herein.

[0062] The coating system described herein is an erosion-resistant thermoset-thermoplastic composite having low storage modulus (E’). In an embodiment, the storage modulus is less than about 4000 MPa, preferably 1000 to 3000 MPa at 25°C. The erosion-resistant coating system as described herein may also be characterized in terms of the ratio of the loss modulus (E”) and the storage modulus (E’) of the coating. This is also expressed as tan 5, and for the system described herein, optimal tan 5 are about 0.01 to 0.3, preferably below 0.1 at 25°C. [0063] In particular, the erosion-resistant coating system is a thermoplastic composite with low storage modulus (E’) that remains stable over time on exposure to produced water. As used herein, the term “produced water” is a term used in the oil, gas, and geothermal industry to describe water that is produced as a byproduct during the extraction of oil and natural gas or used as a medium for heat extraction. Water that is produced along with the hydrocarbons is generally brackish and saline water in nature and tends to cause more corrosion and/or erosion of the substrate material. Therefore, an effective erosion-resistant system must be impermeable or resistant to the effects of produced water and show little to no change to the storage modulus over time when exposed to erosive conditions. As seen in Figure 6, the erosion-resistant coating described herein shows almost no change in storage modulus (E’) after prolonged exposure of more than 30 minutes to produced water, in contrast to a commercially available thermoplastic coating system (nylon) shown for comparison.

[0064] The erosion-resistant coating system described herein demonstrates erosion performance comparable to an uncoated steel substrate on exposure to produced water. Erosion performance is determined according to the methods described in ASTM G76-18 (Standard Test Method for Conducting Erosion Tests by Solid Particle Impingement Using Gas Jets). Sample or test substrates coated with the erosion-resistant coating system described herein show the same rate of erosion as a blank steel sample used as a control (see Figure 4). [0065] The erosion performance of the coating system described herein may also be determined by immersion testing. In an aspect, the erosion-resistant coating system described herein demonstrates optimal immersion resistance at 140F (60°C) following at least 28 days of exposure to produced water, both in unstirred and stirred conditions. The stirred conditions are meant to simulate the flow or movement of liquid and gas in a pipeline and provide a more effective measure of the erosion resistance of the coating system. As shown in Figure 5, the erosion-resistant coating system as described herein (Coating #5) has a much lower rate of erosion following immersion testing than a commercially available coating system (Coating #3, nylon) shown for comparison.

[0066] The erosion performance of the coating system described herein may also be determined by autoclave testing according to the methods described in NACE TM0185 (Evaluation of Internal Plastic Coatings for Corrosion Control of Tubular Goods by Autoclave Testing). In an aspect, the erosion-resistant coating system described herein demonstrates optimal autoclave performance at 140F (60°C) and 800 psi (5.51 MPa) following at least 28 days of exposure to produced water, both in unstirred and stirred conditions. The stirred conditions are a modification to the standard NACE TM0185 and are meant to simulate the flow or movement of liquid and gas in a pipeline and provide a more effective measure of the erosion resistance of the coating system.

[0067] The present description also provides methods for making a coated article with the erosion-resistant coating described herein applied thereon. The method includes the step of providing a substrate, such as the inner surface of a steel pipe, for example. This is followed by a step of heating the substrate to a temperature of about 150°C to 200°C, preferably about 170°C to 180°C for about 60 minutes. A first coating is formed on the substrate by applying a first composition to the substrate to provide corrosion resistance. The first coating may be a powder coating or a liquid coating, preferably a FBE powder coating. An erosion-resistant coating is formed over the first coating by applying a powder thermoplastic coating derived from a modified polyolefin over the first composition. In an aspect, the second coating is applied over the first coating immediately, i.e., when the first coating is substantially uncured. The first and second coating compositions are then cured together under conditions effective to form a cured coating (thermoset-thermoplastic composite coating), i.e., by heating the coated substrate to a temperature of about 220°C to 240°C, preferably 232°C for 30 to 60 minutes, and then allowing the coated substrate to cool. In an alternative aspect, the second coating is applied over the first coating after the first coating is substantially cured. In an aspect, the substrate may first be cleaned or treated to remove surface impurities, by sandblasting, for example prior to heating and applying the first coating composition. In another aspect, the substrate may have a primer applied thereon, preferably a liquid phenolic primer, before the first coating composition is applied.

[0068] In an embodiment, the second coating composition is applied over the first composition in a single pass, i.e., only one layer of the second coating composition is applied. In another embodiment, the second coating composition is applied over the first composition in multiple passes, preferably 2 to 6 passes, or the number of passes required to reach optimal dry film thickness (DFT) of 20 to 100 mil (approximately 500 pm to 2540 pm) for the entire erosion-resistant composite system. In one aspect, the second coating has a DFT of 20 to 80 mils, 35 to 80 mils, and 35 to 60 mils.

[0069] The first coating composition described herein, preferably a powder composition, may be applied to a substrate, such as the inner surface of a steel pipe, for example, by various means known to those of skill in the art, including the use of fluid beds and spray applicators. Most commonly, an electrostatic spraying process is used, wherein the particles are electrostatically charged and sprayed onto a substrate that has been grounded so that the powder particles are attracted to and cling to the article. The coating is then cured, either before or after application of a second coating composition, and such curing may occur via continued heating, subsequent heating, or residual heat in the substrate. For example, the coating may be applied to a heated substrate such that curing occurs in a continuous manner. [0070] The second coating, preferably a powder coating, is applied over the first coating by various means known to those of skill in the art, including electrostatic spray application, or fluidized bed coating application. Typically, a spray application process is used, where the second coating is electrostatically applied over the first coating before the first coating is gelled or cured. The coated substrate is then heated after the second coating is applied to allow both the first and second coating compositions to be in a molten or flowing state at the same time, thereby increasing crosslinking and interlayer adhesion and producing a molecular composite that is effective as an erosion-resistant coating system.

[0071] The erosion-resistant coating system described herein may be applied over a wide variety of substrates, including steel substrates used in the transport of oil, gas, and other substances. In a preferred aspect, the erosion-resistant coating system described herein is applied over a tubular good. The phrase “tubular good” may refer, without limitation, to rolled metal products used in the production of oil and gas. Examples include, without limitation, drill pipe, line pipe, casing, lining, coupling, connectors, production tubing, delivery tubing, elbows, straight pipe sections, spools, and other accessories or combinations thereof used in the production of oil and gas. These products are manufactured in different grades and in different sizes and lengths according to specifications provided by the American Petroleum Institute (API).

EXAMPLES

[0072] The invention is illustrated by the following examples. It is to be understood that the particular examples, materials, amounts, and procedures are to be interpreted broadly in accordance with the scope and spirit of the inventions as set forth herein. Unless otherwise indicated, all parts and percentages are by weight and all molecular weights are weight average molecular weight (Mw) and is measured by methods known to those of skill in the art, preferably gel permeation chromatography (GPC) or size exclusion chromatography (GPC/SEC). Unless otherwise specified, all chemicals used are commercially available from, for example, Sigma-Aldrich, St. Louis, Missouri.

TEST METHODS

[0073] Unless indicated otherwise, the following test methods were utilized in the Examples that follow.

Dry and Wet Erosion Testing [0074] To test for erosion resistance of the coating systems described herein, a modified version of ASTM G76 (Solid Particle Impingement Erosion Test) is used. A micro-abrasive or micro-blaster cabinet is used with a 30-degree angle of impingement and a distance of the test sample of about 2 in (5.1 cm) from the blaster nozzle tip. Silica particles (500 g) are expelled at an air pressure setting of 28 psi and a desired velocity of 30 m/s and allowed to impinge on the surface of the coated tests panels or uncoated steel test panels (control). Coated samples are either exposed to 500 g of silica sand or until the coating film eroded to the substrate surface, whichever happens first.

Erosion Depth Measurement

[0075] To assess the depth of erosion craters formed on the test samples, a profilometry technique using the Keyence VHK-7000 series microscope is used. The microscope begins by focusing on one end of the test sample, collecting an image, and then moving to successive locations on the test sample to take more images. These images are then collated into a composite in-focus image of the sample that can be used to measure the depth of erosion craters (Zc) on the test sample relative to a steel control or blank (Zs). The erosion rates of the steel control (Es) and of the test samples (Ec) are calculated by dividing the depth of the crater by the weight of the silica sand that created the crater, as demonstrated by the equations below. Erosion measurements are taken on coated panels in a cured (dry) state and post-exposure (wet) state. Use of this method is illustrated in Figures 1-3.

Dynamic Mechanical Analysis (DMA) Testing [0076] To compare the structure of various coatings described herein as a function of temperature, free films are made and tested by ASTM D5026-15 (Standard Test Method for Plastics: Dynamic Mechanical Properties: In Tension). Test specimens approximately 2.54 mm x 5 mm were cut from the free films and tested by DMA using standard commercially available analyzers, such as TA Instruments Q850, for example. Testing is conducted at 1 Hz with 0.05% to 0.2% strain at a pretension force from 0.05N to 0.1 N as the films are heated from -20°C through the glass transition temperature (Tg) at a rate of 3°C per minute. This allows comparison of the elastic modulus, E’ and their ratio of energy dissipation, E”/E’ or tan delta (5) of the film as a function of temperature.

[0077] DMA curves are used to compare the structure of multiple coatings. The glass transition temperature (Tg), where the coating changes from a glassy to a rubbery material with a significant increase in free volume, is noted first by a decrease in E,’ at the middle by a peak in E,” and by a peak in the tan 5 curve near the end. Above the Tg, there may be a flat region in the E’ curve often called the plateau modulus. This modulus value is often indicative of the crosslink density of a material. Equivalent systems with a higher E’ plateau will usually provide better barrier performance provided they also have good adhesion and flexibility. Results of DMA testing for erosion-resistant coatings is illustrated in Figures 7 and 8.

[0078] In addition to dry air (dry erosion) testing, specimens from the coating free films are assessed for wet erosion performance by DMA using standard commercially available solids analyzers, such as the TA Instruments RSA-G2, for example. Film tension fixtures and a submersion apparatus are used to assess samples immersed in either deionized water or produced water, and testing is conducted isothermally at 60°C (140°F) at 1 Hz frequency, 0.1% strain and 0.1 N pretension. After a 2-minute preconditioning in air, the test fluid, (preheated to 60°C (140°F)) is added so the film plasticization can be observed through the modulus drop over a 30-minute test duration. Immersion testing can be used to compare the effects of plasticization on mechanical properties. Significant changes seen could portend even larger changes in the field where the exposure is over longer times and at greater pressures. Results for DMA testing of immersed erosion-resistant coatings is illustrated in Figure 6.

Hardness of Coatings

[0079] To measure the Martens hardness (an indication of the elastic or plastic nature of the coating) described herein, a micro-indenter (such as Fischerscope HM2000, for example) is used as described by EN ISO: 14577-1 (Metallic Materials - Instrumented indentation test for hardness and materials parameters) and coated test panels are used in dry, ambient conditions of 23°C temperature and relative humidity of 25%. A Vickers indenter is lowered into the coating applied to a test panel to a force of 20 mN, held for 5 seconds and then removed. The contact area for indentation is from 1 to 4 p² and to a depth of up to about 3 pm. Results for micro-indenter testing of erosion resistant coatings is illustrated in Figure 9.

Immersion Testing

[0080] To simulate field conditions, coated test panels are subjected to immersion testing in produce water under continuous agitation at temperatures of about 60°C. The test panels are placed in a panel holder immersed in a mixing vessel containing an 80/20 by volume mixture of production water and kerosene (i.e., “produced water”), using separate samples for each time interval. After a given period of time (14, 21, or 28 days), the samples are removed from the water, wiped dry, and then subjected to erosion testing.

Autoclave Testing

[0081] In order to assess performance after exposure, metal test panels are coated with a one- component (IK) primer at a dry film thickness of 0.12 to 18 pm and then further coated with the coatings described herein. The coatings are allowed to cure, and coated panels are assessed for cure using differential scanning calorimetry (DSC). The coated panels are then placed in autoclave conditions for 28 days at 60°C at varying pressures of 100 psi (7 day), 200 psi (14 day), 400 psi (21 day) and 800 psi (28 day). At seven-day intervals, the coated panels are reviewed for appearance, adhesion, swelling, and blistering. ASTM D6677-18 (Standard Test Method for Evaluating Adhesion by Knife) is used to assess adhesion between the first coating and the second coating. A rating of 6-10 is considered acceptable for the erosion-resistant coating. If no appreciable changes are seen, the test panels are returned to the autoclave for an additional seven days at a higher pressure.

EXAMPLE 1: Coating Formulations

[0082] Various coating compositions as shown in Table 1 were applied to metal test panels (1.5 in x 3 in x 1/8 in) with a 50 to 100 pm blast profile. Coated panels were then exposed to dry and wet erosion conditions and then assessed for appearance and performance. Table 1. Coating Formulations

EXAMPLE 2: Evaluation of Erosion Performance

[0083] The test formulations of Example 1 were evaluated for erosion resistance as described in the test methods above. In order to be an effective erosion coating, each formulation must adhere to the substrate while not swelling or blistering on exposure to produced water or other simulated field situations. In addition, an effective coating is one that passes the autoclave test as described above.

[0084] Results of various performance evaluations are as depicted in Figure 4 (rate of erosion relative to bare steel), Figure 5 (DMA comparison of immersion testing for coatings #3 and #5), Figure 6 (storage modulus following immersion testing), Figure 7 (storage modulus as a function of temperature), Figure 8 (tan 5), and Figure 9 (hardness following autoclave testing).

EXAMPLE 3: Erosion-Resistant Coating Application

[0085] A metal test substrate was heated to 350F (177°C) for 60 minutes, and a FBE coating was then electrostatically applied to the substrate, immediately followed by application of a thermoplastic powder topcoat. The multi-layer coated substrate was cured in an oven at 450F (232°C) for 30 to 75 minutes and then allowed to cool to room temperature (23°C).

[0086] The complete disclosure of all patents, patent applications, and publications, and electronically available material cited herein are incorporated by reference. The foregoing detailed description and examples have been given for clarity of understanding only. No unnecessary limitations are to be understood therefrom. The invention is not limited to the exact details shown and described, for variations obvious to one skilled in the art will be included within the invention defined by the claims. The invention illustratively disclosed herein suitably may be practiced, in some embodiments, in the absence of any element which is not specifically disclosed herein.

Claims

WHAT IS CLAIMED IS:

1. A coating system, comprising: a first coating applied to a substrate; and a second coating applied over the first coating, the second coating comprising a thermoplastic component, wherein the coating system is erosion resistant.

2. An erosion-resistant coating system, comprising: a first coating applied to a substrate, wherein the first coating is corrosion resistant; and a second coating applied over the first coating, the second coating comprising a thermoplastic component.

3. A method of coating a substrate, comprising providing a substrate; contacting at least one surface of the substrate with the coating system of any of the above claims; subjecting the substrate with coating system applied thereon to conditions effective to form a cured coating on the substrate.

4. A coated article, comprising a substrate; a coating system according to any of the above claims applied to the substrate according to the method of any of the above claims.

5. The coating system, method, or article of any of the above claims, optionally comprising a primer coating applied to the substrate prior to application of the first coating.

6. The coating system, method, or article of any of the above claims, optionally comprising a liquid phenolic primer coating applied to the substrate prior to application of the first coating.

7. The coating system, method, or article of any of the above claims, wherein the first coating applied to the substrate comprises a binder component selected from epoxy, polyester, polyurethane, polyamide, acrylic, polyvinylchloride, nylon, fluoropolymer, silicone, other resins, or combinations thereof.

8. The coating system, method, or article of any of the above claims, wherein the first coating applied to the substrate comprises an epoxy resin binder component.

9. The coating system, method, or article of any of the above claims, wherein the first coating applied to the substrate is a fusion bonded epoxy (FBE) powder coating.

10. The coating system, method, or article of any of the above claims, wherein the first coating applied to the substrate is a thermoplastic component.

11. The coating system, method, or article of any of the above claims, wherein the first coating applied to the substrate is a thermoset component.

12. The coating system, method, or article of any of the above claims, wherein the second coating applied over the first coating is a polyolefin modified with at least one a,P- unsaturated carboxylic acid or acid anhydride thereof.

13. The coating system, method, or article of the any of the above claims, wherein the second coating applied over the first coating is a thermoplastic component selected from polyethylene, polypropylene, acid- or anhydride-modified polyethylene, acid- or anhydride-modified polypropylene, and mixtures of combinations thereof.

14. The coating system, method, or article of any of the above claims, wherein the second coating applied over the first coating is a thermoplastic powder coating.

15. The coating system, method, or article of any of the above claims, optionally comprising a second coating applied over the first coating wherein the second coating is a thermoplastic liquid coating.

16. The coating system, method, or article of any of the above claims, wherein the second coating applied over the first coating is a single layer extruded thermoplastic modified polyolefin film.

17. The coating system, method, or article of any of the above claims, wherein the second coating applied over the first coating is a multilayer extruded thermoplastic film.

18. The coating system, method, or article of any of the above claims, wherein the second coating applied over the first coating is an extruded film of acid- or anhydride- modified polypropylene.

19. The coating system, method, or article of any of the above claims, wherein the second coating applied over the first coating is an extruded film of maleic anhydride- modified polypropylene (PP-MA).

20. The coating system, method, or article of any of the above claims, wherein the second coating applied over the first coating is a maleic anhydride-modified polypropylene (PP-MA) powder coating.

21. The coating system, method, or article of any of the above claims, wherein the second coating is an extruded thermoplastic film that is applied over the first coating to obtain a composite with a low modulus.

22. The coating system, method, or article of any of the above claims, wherein the second coating is an extruded thermoplastic film that is applied over the first coating to obtain a composite with storage modulus (E’) that remains stable over time on exposure to produced water.

23. The coating system of any of the above claims, wherein the coating system applied to a substrate demonstrates erosion performance comparable to uncoated steel on exposure to produced water.

24. The coating system of any of the above claims, wherein the coating system applied to a substrate demonstrates erosion performance comparable to uncoated steel on exposure to produced water when tested according to ASTM G76.

25. The coating system of any of the above claims, wherein the coating system demonstrates optimal immersion resistance at 60°C for at least 28 days in produced water.

26. The coating system of any of the above claims, wherein the coating system demonstrates optimal autoclave performance at 60°C and 800 psi in a two-phase system for up to 28 days when tested in accordance with NACE TM0185.

27. The coating system of any of the above claims, wherein the first coating has dry film thickness (DFT) of about 6 to 20 mil.

28. The coating system of any of the above claims, wherein the first coating has dry film thickness (DFT) of about 8 to 16mil.

29. The coating system of any of the above claims, wherein the first coating has dry film thickness (DFT) of about 10 to 14 mil.

30. The coating system of any of the above claims, wherein the second coating has dry film thickness of about 30 to 65 mil.

31. The coating system of any of the above claims, wherein the second coating has dry film thickness of about 20 to 100 mil.

32. The coating system of any of the above claims, wherein the second coating has dry film thickness of about 35 to 80 mil.

33. The coating system of any of the above claims, wherein the first and second coating together form a molecular composite coating system.

34. The coating system of any of the above claims, wherein the second coating is an extruded film derived from maleic anhydride-modified polypropylene (PP-MA) having particle size (D90) of 230 to 250 pm as determined by sieve analysis according to ASTM D1921-18.

35. The coating system of any of the above claims, wherein the second coating is an extruded film derived from maleic anhydride-modified polypropylene (PP-MA) having particle size (D90) of 390 to 410 pm as determined by laser diffraction.

36. The coating system of any of the above claims, wherein the first coating is a film derived from fusion bonded epoxy (FBE) having particle size (D90) of 110 to 130 pm as determined by laser diffraction.

37. The coating system of any of the above claims, wherein the first coating is a film derived from fusion bonded epoxy (FBE) and having porosity of about 1 to 4, when tested according to CSA Z2245. 20.

38. The coating system of any of the above claims, wherein the second coating is a film derived from maleic anhydride-modified polypropylene (PP-MA) and having porosity of about 1 to 4, when tested according to CSA Z2245. 20.

39. The coating system of any of the above claims, wherein the system is applied to at least an inner diameter of a substrate, wherein the substrate is at least one tubular good.

40. The coating system of any of the above claims, wherein the system is applied to at least an outer diameter of a substrate, wherein the substrate is at least one tubular good.

41. The coating system or method of any of the above claims, wherein the first coating is applied to the substrate in one application.

42. The coating system or method of any of the above claims, wherein the second coating is applied to the substrate in at least one application.

43. The coating system or method of any of the above claims, wherein the second coating is applied to the substrate in at least two applications.

44. The coating system or method of any of the above claims, wherein the substrate is heated to a temperature of at least 3 OOF (149°C) before applying the first coating composition.

45. The coating system or method of any of the above claims, wherein the substrate is heated to about 450F (232C) after first and second coatings have been applied.

46. The coating system or method of any of the above claims, wherein the first coating composition is corrosion-resistant, as determined by CSA Z245.20.