Elastomer Erosion Coating System

Abstract

Described herein is a coating system that has better erosion resistance than steel when exposed to silica or sand. The system includes a thermosetting resin as a base coat, with a thermoplastic top coat applied over the base coat. Optionally, a liquid primer can be applied to the substrate before application of the base coat. Methods of making and using the coating system are also described herein.

Description

[Technical Field]

[0001] Components utilized in oil field operations, such as pipelines used in fracking wells, are often exposed to harsh environments. These components are subjected to high flow rates, high pressures, and other environmental conditions. Crude oil contains corrosive components such as carbon dioxide (CO2), hydrogen sulfide (H2S), organic acids, dissolved gases, and brine. Oil sands contain CO2 and chloride ions (Cl - ), bicarbonate ion (HCO3 - ), sulfate ions (SO4 2- In some extraction methods, sand can mix with the flowing fluid to form a multiphase solid-liquid mixture. The flowing mixture in components such as piping and elbows, and pump impellers, can lead to solid particle erosion along with corrosion. Erosion and corrosion can shorten equipment life due to higher rates of material loss, resulting in replacement and downtime.

[0002] Standard fusion-bonded epoxy (FBE) powder coatings are frequently used in the oil and gas industry to coat and protect surfaces and components and are known to provide effective corrosion resistance. These coatings are sometimes also used as erosion-resistant coatings. 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 solid and corrosive materials flowing through these components at high pressures and temperatures. The combination of erosion and erosion / corrosion significantly shortens the lifespan of equipment used in the industry, resulting in high rates of material loss and high costs associated with repairs and production shutdowns.

[0003] From the foregoing, it can be appreciated that what is needed in the art is a coating system for use in the oil and gas industry that is resistant to both corrosion and erosion. Such a coating system, as well as methods for preparing and using the same, are disclosed and claimed herein. Summary of the Invention

[0004] The present invention provides an erosion-resistant coating system. In one embodiment, the coating system includes a first coating applied to a substrate and a second coating applied over the first coating, the second coating including a thermoplastic component, and the coating system is erosion-resistant.

[0005] In another embodiment, the present disclosure provides a method of coating a substrate. The method includes 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 thereto to conditions effective to form a cured coating on the substrate. The erosion-resistant coating system includes a first coating applied to the substrate and a second coating applied over the first coating, the second coating including a thermoplastic component.

[0006] In yet another embodiment, the present disclosure provides a coated article comprising a substrate having an erosion resistant coating system applied thereto, the erosion resistant coating system comprising a first coating applied to the substrate and a second coating applied over the first coating, the second coating comprising a thermoplastic component.

[0007] The above "Summary" of the present invention is not intended to describe each disclosed embodiment or every implementation of the present invention. The following description more particularly exemplifies exemplary embodiments. In several places throughout the application, guidance is provided through lists of examples, which examples 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.

[0008] The details of one or more embodiments of the invention are set forth 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 explanation of the drawings]

[0009] [Figure 1] 1 shows a microscope image of the top view of a coated eroded panel. [Figure 2] 1 shows a microscope image of a side view of a coated eroded panel. [Figure 3] 1 shows profile and depth measurements of a coated eroded panel. [Figure 4] 1 is a graphical representation of the erosion rate of a coating relative to bare steel. [Figure 5] 1 is a graphical representation of the average erosion rate of a coating against steel. [Figure 6] 1 is a graphical representation of the storage modulus (E') after an immersion test. [Figure 7] 1 is a graphical representation of storage modulus (E') as a function of temperature. [Figure 8] 1 is a graphical representation of the E'' / E' ratio (tan δ). [Figure 9] 1 is a graphical representation of coating hardness for several coatings.

[0010] Selected Definitions Unless otherwise stated, the following terms used herein have the meanings provided below.

[0011] The term "component" refers to any compound that contains a particular characteristic or structure. Examples of components include chemical compounds, monomers, oligomers, polymers, and organic groups contained therein.

[0012] 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 herein 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 of the component, based on the total weight of the composition.

[0013] The term "crosslinker" refers to a molecule that can form covalent bonds between polymers or between two different regions of the same polymer.

[0014] The term "particle size" as used herein refers to particle size distribution, i.e., the frequency of particles of a particular size in a sample of a component of the compositions described herein (such as a powder, granules, or suspension). Particle size may be described as D50 (average particle size), D90 (the particle size diameter at which 90% of the distribution has a smaller particle size and 10% has a larger particle size), or D10 (the particle size diameter at which 10% of the distribution has a smaller particle size and 90% has a larger particle size). Particle size may be determined or analyzed by various methods known to those skilled in the art, including laser diffraction (LD), dynamic light scattering (DLS), dynamic image analysis (DIA), or sieve analysis. Unless otherwise specified, particle sizes described herein are determined by dynamic light scattering or otherwise provided by the manufacturer of a particular component.

[0015] As used herein, the term "erosion" refers to damage to a material caused by mechanical movement or impact between particles and a surface. Specifically, as defined by NACE International, "erosion" means "the progressive loss of material from a solid surface resulting from mechanical interaction between the solid surface and a fluid, a multi-component fluid, or solid particles carried with the fluid." These particles may be present, for example, in a liquid, a slurry, or as particles suspended in a liquid or slurry. When these particles impact a surface at high speed, material is removed from the surface. This is in contrast to "wear," a term that refers to damage to a material caused by friction when one material rubs against another and material is scraped off the surface. Thus, 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.

[0016] The term "self-crosslinking," when used in the context of a self-crosslinking polymer, refers to the ability of the polymer to enter into a crosslinking reaction with itself and / or another molecule of the polymer to form a covalent bond between them in the absence of an external crosslinking agent. Typically, this crosslinking reaction occurs through the reaction of complementary reactive functional groups present on the self-crosslinking polymer itself, or two separate molecules of the self-crosslinking polymer.

[0017] The term "thermoplastic" refers to a material that melts and changes shape when heated sufficiently and hardens when cooled sufficiently. Such materials can typically undergo repeated melting and hardening without exhibiting any appreciable chemical change. In contrast, "thermoset" refers to a material that is crosslinked and does not "melt."

[0018] Unless otherwise indicated, reference to a "(meth)acrylate" compound (the "meth" is in parentheses) is meant to include both acrylate and methacrylate compounds.

[0019] When the term "on" is used in the context of a coating applied "on" a surface or substrate, it includes both a coating 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.

[0020] Unless otherwise indicated, the term "polymer" includes both homopolymers and copolymers (ie, polymers of two or more different monomers).

[0021] The terms "comprises" and variations thereof do not have a limiting meaning where these terms appear in the description and claims.

[0022] The terms "preferred" and "preferably" refer to embodiments of the invention that may offer 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.

[0023] As used herein, "a," "an," "the," "at least one," and "one or more" are used interchangeably. Thus, for example, a coating composition that includes "an" additive can be interpreted to mean that the coating composition includes "one or more" additives.

[0024] Also herein, when numerical ranges are specified by endpoints, they include all numbers within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.). Furthermore, the disclosure of a range includes the disclosure of all subranges within that broader range (e.g., 1 to 5 discloses 1 to 4, 1.5 to 4.5, 1 to 2, etc.). DETAILED DESCRIPTION OF THE INVENTION

[0025] The present disclosure provides erosion-resistant coating systems. The coating systems include a first coating applied to a substrate and at least a second coating applied over the first coating, the second coating being a thermoplastic composition. Erosion-resistant coating systems of the type described herein exhibit erosion performance similar to that of steel when exposed to certain substances, including, for example, sand. These coating systems also have excellent adhesion and appearance and do not blister or swell when exposed to corrosive environments.

[0026] In some embodiments, the present disclosure provides an erosion-resistant coating system comprising a first coating applied to a substrate. In one aspect, the first coating is applied to a substrate, optionally to a substrate that has a primer coating applied thereto. In a preferred aspect, the first coating is erosion-resistant. In one aspect, the first coating is thermoplastic. In another aspect, the first coating is thermosetting. In one aspect, the first coating can be a one-component coating. In another aspect, the first coating can be a two-component coating. In yet another aspect, the first coating can be a liquid coating, and in yet another aspect, the first coating can be a powder coating.

[0027] The first coating is derived from a coating composition including at least one binder resin component, which in one embodiment is selected from epoxy, polyester, polyurethane, polyamide, acrylic, polyvinyl chloride, nylon, fluoropolymer, silicone, other resins, or combinations thereof.

[0028] In a preferred embodiment, the binder resin component is an epoxy or polyepoxide binder resin component. Suitable epoxy resin components or polyepoxides preferably contain at least two 1,2-epoxide groups per molecule. In one embodiment, the epoxy equivalent weight is preferably about 100 to about 4000, more preferably about 500 to 1000, based on the total solids content of the polyepoxide. The polyepoxide may be aliphatic, alicyclic, aromatic, or heterocyclic. In one embodiment, the polyepoxide may contain substituents such as halogens, hydroxyl groups, ether groups, etc.

[0029] Suitable epoxy resin compositions or polyepoxides for use in the compositions and methods described herein include, but are not limited to, epoxy ethers formed by the reaction of epihalohydrins, such as epichlorohydrin, with polyphenols, typically and preferably in the presence of 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, and 1,5-hydroxynaphthalene. Bisphenol A and diglycidyl ethers of bisphenol A are preferred.

[0030] Suitable epoxy resin compositions or polyepoxides can also include polyglycidyl ethers of polyhydric alcohols. These compounds can be derived from polyhydric alcohols such as ethylene glycol, propylene glycol, butylene glycol, 1,6-hexylene glycol, neopentyl glycol, diethylene glycol, glycerol, trimethylolpropane, and pentaerythritol. Other suitable epoxides or polyepoxides include polyglycidyl esters of polycarboxylic acids formed by reacting epihalohydrins or other epoxy compositions with aliphatic or aromatic polycarboxylic acids, such as succinic acid, adipic acid, azelaic acid, sebacic acid, maleic acid, fumaric acid, phthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, and trimellitic acid. In one embodiment, dimerized unsaturated fatty acids can also be reacted with polymeric polycarboxylic acids to produce polyglycidyl esters of polycarboxylic acids.

[0031] In one embodiment, the epoxy resin compositions or polyepoxides described herein are derived by oxidation of an ethylenically unsaturated alicyclic compound. The ethylenically unsaturated alicyclic compound may be epoxidized by reaction with oxygen, perbenzoic acid, acid-aldehyde monoperacetate, peracetic acid, or the like. Polyepoxides produced by such reactions are known to those skilled in the art and include, but are not limited to, epoxy alicyclic ethers and esters.

[0032] In one embodiment, the epoxy resin composition or polyepoxide described herein comprises an epoxy novolac resin obtained by the reaction of an epihalohydrin with the condensation product of an aldehyde and a monohydric or polyhydric phenol. Examples include, but are not limited to, the reaction product of epichlorohydrin with the condensation product of formaldehyde and various phenols (e.g., phenol, cresol, xylenol, butylmethylphenol, phenylphenol, biphenol, naphthol, bisphenol A, bisphenol F, etc.).

[0033] In one embodiment, the first coating composition described herein is a powder coating composition. Thermosetting materials are generally preferred for use as polymer binders in powder coating applications. The powder compositions described herein are curable compositions that include at least one curing agent. In one embodiment, the curing agent described herein is useful for obtaining a solid, flexible, epoxy-functional powder composition. Suitable curing agents include, for example, epoxide-functional compounds (e.g., triglycidyl isocyanurate), hydroxyalkylamides (e.g., β-hydroxyalkylamides commercially known as PRIMID), blocked isocyanates or uretdiones, amines (e.g., dicyandiamide), dihydrazides (e.g., adipic dihydrazide (ADH), isophthalic dihydrazide (IDH), sebacic dihydrazide (SDH), etc.), phenol-functional resins, carboxyl-functional curing agents, and the like. The curing reaction can be induced thermally or by exposure to radiation (eg, UV, UV-vis, visible light, IR, near IR, and e-beam).

[0034] In one aspect, the curing agent is selected to be compatible with the epoxy resin composition and to act to cure the powder composition at the temperatures used to cure and apply the powder composition. Thus, for the powder compositions described herein, the curing agent is preferably selected to have a melting or softening point within the application temperatures described herein, i.e., preferably between about 150°C and 300°C, more preferably between about 220°C and 260°C.

[0035] Thus, in a preferred embodiment, the powder compositions described herein are fusion bonded epoxy (FBE) compositions. Preferred compositions include epoxy resins prepared from a homogeneous mixture of a polyglycidyl ether of a polyhydric phenol and a dihydrazide or dicyandiamide curing agent. In one aspect, the fusion bonded epoxy composition is present in an amount of about 20-90 wt%, preferably about 30-80 wt%, more preferably about 40-70 wt%, and most preferably about 50-60 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) and the CORVEL line of products (Akzo Nobel).

[0036] Suitable FBE powder compositions for use herein include compositions having particle sizes of about 5-20 μm, preferably 10-15 μm (D10), about 40-70 μm, preferably 50-60 μm (D50), and about 100-140 μm, preferably 110-130 μm (D90), as measured by dynamic light scattering analysis.

[0037] The first coating of the system described herein is a cured film derived from an FBE powder composition. Suitable FBE powder compositions for use herein include those with high porosity resistance. Without being limited by theory, it is believed that higher porosity resistance provides better corrosion protection by minimizing moisture penetration into the substrate. Thus, a highly porosity-resistant 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 evaluated by methods known to those skilled in the art, preferably by methods described in the standard CSA Z245.20 series (Plant-applied External Coatings for Steel Pipe). Thus, in one embodiment, the first coating of the system described herein is a cured film having a porosity rating of about 1 to 4, preferably 1 to 2, as determined by CSA Z245.20, with rating 1 indicating the lowest porosity and rating 5 indicating the highest porosity.

[0038] The first coating of the system described herein is a corrosion-resistant coating. The corrosion resistance of the coating described herein can be determined by standard methods known to those skilled in the art, including measuring cathodic disbonding according to the method described in CSA Z245.20 (Plant-Applied External Coatings for Steel Pipe). A coating is considered to have optimal corrosion resistance if it exhibits less than 15 mm of coating loss after 28 days of exposure at 65°C.

[0039] Without being limited by theory, the corrosion resistance of the first coating, preferably the FBE powder coating, depends in part on the application temperature. At the appropriate application temperature, the spray-applied FBE powder coating melts, flows into the blast profile of the substrate, and then hardens to form a durable coating with minimal porosity and optimal corrosion resistance. If the application temperature is too high, pores, i.e., voids where the film is not continuous, are more likely to form, which can make the substrate more permeable to water and lead to corrosion of the substrate. On the other hand, if the application temperature is too low, the sprayed FBE powder may not melt sufficiently, resulting in poor adhesion. By fine-tuning the application temperature, it is possible to reduce the porosity of the applied FBE coating and obtain a coating with optimal corrosion resistance.

[0040] Thus, in one embodiment, the first coating of the erosion resistant system described herein is applied to a substrate at a temperature of about 300° F. to 375° F. (approximately 149° C. to 191° C.), preferably 325° F. to 350° F. (approximately 163° C. to 177° C.). In one aspect, the substrate is heated to the desired temperature, and then the first coating is applied to the heated substrate, causing the composition to melt, flow, and flatten over the surface of the substrate.

[0041] As described herein, the first coating may be applied at a dry film thickness (DFT) appropriate for the anticipated end use of the substrate. Thus, in one embodiment, the first coating is applied at a DFT of about 6-20 mils (approximately 152 μm-508 μm), preferably about 8-16 mils (approximately 203 μm-406 μm), and more preferably about 10-14 mils (approximately 254 μm-356 μm).

[0042] 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 an unprimed, pretreated, or clean-blasted substrate surface. The primer is intended to be a corrosion-resistant coating applied to metal, and the first coating of the erosion-resistant system described herein is then a basecoat applied over the primer layer. The primer can be a powder coating or a liquid coating. However, the primer coating or primer layer is optional, and the first coating or basecoat can be applied directly to an unprimed, pretreated, or clean-blasted substrate surface without a primer coating. If used, the primer layer can include, for example, a phenolic primer, such as a phenol-formaldehyde resin or an epoxy-phenolic resin.

[0043] In some embodiments, the present disclosure provides an erosion-resistant coating system comprising a second coating applied to a substrate. In one aspect, the second coating is applied to a substrate to which a first coating has been applied. In another aspect, the second coating is applied directly to a substrate to which no first coating has been applied. In a preferred aspect, the second coating is an erosion-resistant coating. In one aspect, the second coating is thermoplastic. In another aspect, the second coating is thermosetting. In one aspect, the second coating can be a one-component coating. In another aspect, the second coating can be a two-component coating. In yet another aspect, the second coating can be a liquid coating, and in yet another aspect, the second coating can be a powder coating.

[0044] In a preferred embodiment, the erosion-resistant second coating is a thermoplastic coating, preferably a powder coating composition, comprising at least one binder resin component. In one aspect, the binder resin component is a polyolefin selected from polyethylene, polypropylene, and the like, and mixtures or combinations thereof.

[0045] In a preferred embodiment, the polyolefin is a modified component, preferably an acid-modified component, obtained by combining the polyolefin with at least one α,β-unsaturated carboxylic acid or anhydride thereof, such as maleic acid, itaconic acid, citraconic acid, anhydrides thereof, or mixtures or combinations thereof. Among these, the anhydride forms are generally preferred, with maleic anhydride being more preferred. Suitable examples of modified polyolefins as described herein include, but are not limited to, maleic anhydride-modified polypropylene, maleic anhydride-modified propylene-ethylene copolymer, maleic anhydride-modified propylene-butene copolymer, maleic anhydride-modified propylene-ethylene-butene copolymer, etc. These acid-modified polyolefins can be used alone or as mixtures or combinations of two or more modified polyolefins.

[0046] 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 exhibit better adhesion to substrate surfaces, thus forming more effective erosion-resistant coatings and providing effective corrosion resistance and barrier properties. In one aspect, the crystalline PP-MA described herein has a 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.

[0047] In one 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 coatings described herein can be single-layer or multi-layer extruded thermoplastic films.

[0048] The second coating described herein is an erosion-resistant powder coating. Without being limited by theory, it is believed that the particle size (D90) of the second coating is important for effective erosion resistance performance. By maintaining the D90 particle size below about 300 μm, 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 susceptible to erosion and failure when contacted with large particulate matter, such as sand or gravel, encountered during oil and gas drilling operations.

[0049] Thus, in one embodiment, suitable extruded films derived from maleic anhydride modified polypropylene (PP-MA) have particle sizes of about 60-100 μm, preferably 70-90 μm (D10), about 220-260 μm, preferably 230-250 μm (D50), and about 370-420 μm, preferably 390-410 μm (D90), as measured by dynamic light scattering analysis and provided by the manufacturer.

[0050] In another embodiment, the extruded film for the second coating described herein is derived from maleic anhydride modified polypropylene having particle sizes of about 40-90 μm, preferably 50-70 μm (D10), about 120-160 μm, preferably 130-150 μm (D50), and about 220-260 μm, preferably 230-250 μm (D90), as sieved through an 84T mesh and measured by sieve analysis according to ASTM D1921-18.

[0051] Without being limited by theory, it is believed that higher porosity resistance provides better erosion resistance by minimizing areas where contact with large particulate matter can cause erosion or coating loss. Thus, a highly porosity-resistant coating or film is one that has minimal voids or pores on the film surface; i.e., the film has low porosity. Film porosity is determined and evaluated by methods known to those skilled in the art, preferably by methods described in the standard CSA Z245.20 series (Plant-applied External Coatings for Steel Pipe). Thus, in one embodiment, the second coating of the system described herein is a cured film having a porosity rating of about 1 to 4, preferably 1 to 2, as determined by CSA Z245.20, with rating 1 indicating the lowest porosity and rating 5 indicating the highest porosity.

[0052] 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 erosion-resistant coating. Thus, in one embodiment, the second coating is applied at a DFT of about 20-100 mils (approximately 508 μm-2540 μm), preferably about 30-85 mils (approximately 762 μm-1651 μm), and more preferably about 40-60 mils (approximately 1016 μm-1524 μm).

[0053] In one embodiment, the first and second coatings described herein are combined to form the erosion-resistant coating system of the present invention. In one 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 in which two or more coatings are chemically bonded or crosslinked at the interface between them to maximize interlayer adhesion. This molecular composite forms the erosion-resistant coating system described herein.

[0054] The coating systems described herein are erosion-resistant thermoset-thermoplastic composites with a low storage modulus (E'). In one embodiment, the storage modulus is less than about 4000 MPa, preferably 1000-3000 MPa, at 25°C. The erosion-resistant coating systems described herein may also be characterized in terms of the ratio of the coating's loss modulus (E'') to its storage modulus (E'). This is also expressed as tan δ, and for the systems described herein, the optimum tan δ is about 0.01-0.3, preferably less than 0.1, at 25°C.

[0055] In particular, the erosion-resistant coating system is a thermoplastic composite with a low storage modulus (E') that remains stable over time upon exposure to produced water. As used herein, the term "produced water" is used to describe water produced as a by-product during oil and natural gas extraction or used as a medium for heat extraction in the oil, gas, and geothermal industries. Water produced with hydrocarbons is generally brackish and salty in nature and tends to cause more corrosion and / or erosion of substrate materials. Therefore, an effective erosion-resistant system must be impervious or resistant to the effects of produced water and exhibit little or no change in storage modulus over time when exposed to erosive conditions. As can be seen in Figure 6, the erosion-resistant coating described herein exhibits little change in storage modulus (E') after extended exposure to produced water (greater than 30 minutes), in contrast to a commercially available thermoplastic coating system (nylon) shown for comparison.

[0056] The erosion-resistant coating systems described herein exhibit erosion performance comparable to uncoated steel substrates when exposed to produced water. Erosion performance is determined according to the method 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 systems described herein exhibit the same erosion rate as a blank steel sample used as a control (see Figure 4).

[0057] The erosion performance of the coating systems described herein can also be determined by immersion testing. In one aspect, the erosion-resistant coating systems described herein exhibit optimal immersion resistance at 140°F (60°C) after at least 28 days of exposure to produced water in both unstirred and agitated conditions. The agitated conditions are meant to simulate the flow or movement of liquids and gases in a pipeline and provide a more valid measure of the coating system's erosion resistance. As shown in Figure 5, the erosion-resistant coating system described herein (Coating #5) exhibits a much lower erosion rate after immersion testing than a comparable commercially available coating system (Coating #3, nylon).

[0058] The erosion performance of the coating systems described herein may also be determined by autoclave testing according to the method described in NACE TM0185 (Evaluation of Internal Plastic Coatings for Corrosion Control of Tubular Goods by Autoclave Testing). In one aspect, the erosion-resistant coating systems described herein exhibit optimal autoclave performance at 140°F (60°C) and 800 psi (5.51 MPa) after at least 28 days of exposure to produced water in both unstirred and agitated conditions. The agitated conditions are a modification of standard NACE TM0185, meant to simulate the flow or movement of liquids and gases in a pipeline and provide a more valid measure of the erosion resistance of the coating system.

[0059] The present disclosure also provides a method for preparing a coated article having the erosion-resistant coating described herein applied thereto. The method includes providing a substrate, such as the inner surface of a steel pipe. This is followed by 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 can be a powder coating or a liquid coating, preferably an FBE powder coating. An erosion-resistant coating is formed on the first coating by applying a powder thermoplastic coating derived from a modified polyolefin over the first composition. In one embodiment, a second coating is applied immediately over the first coating, i.e., while 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 cooling the coated substrate. In an alternative embodiment, after the first coating is substantially cured, the second coating is applied over the first coating. In one embodiment, the substrate may first be cleaned or treated to remove surface impurities, for example, by sandblasting, before heating and applying the first coating composition. In another embodiment, the substrate may have a primer, preferably a liquid phenolic primer, applied thereto before the first coating composition is applied.

[0060] In one embodiment, the second coating composition is applied in a single pass over the first composition, 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 as many passes as necessary to achieve an optimum dry film thickness (DFT) of 20 to 100 mils (approximately 500 μm to 2540 μm) 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.

[0061] The first coating composition described herein, preferably a powder composition, can be applied to a substrate, such as the interior surface of a steel pipe, by a variety of means known to those skilled in the art, including the use of fluidized bed and spray applicators. Most commonly, an electrostatic spray process is used, in which particles are electrostatically charged and sprayed onto a grounded substrate so that the powder particles are attracted to and adhere to the article. The coating is then cured either before or after application of the second coating composition; such curing can occur by continuous heating, subsequent heating, or residual heat in the substrate. For example, the coating may be applied to a heated substrate so that curing occurs continuously.

[0062] The second coating, preferably a powder coating, is applied over the first coating by various means known to those skilled in the art, including electrostatic spray application or fluidized bed coating. Typically, a spray application process is used, with the second coating electrostatically applied over the first coating before the first coating has gelled or cured. After the second coating is applied, the coated substrate is then heated to simultaneously melt or flow both the first and second coating compositions, thereby enhancing crosslinking and interlayer adhesion and creating a molecular composite useful as an erosion-resistant coating system.

[0063] The erosion-resistant coating systems described herein can be applied to a wide variety of substrates, including steel substrates used in the transportation of oil, gas, and other materials. In a preferred embodiment, the erosion-resistant coating systems described herein are applied to tubular products. The term "tubular products" may refer, without limitation, to rolled metal products used in oil and gas production. Examples include, but are not limited to, drill pipe, line pipe, casing, linings, couplings, connectors, production tubing, delivery tubing, elbows, straight pipe sections, spools, and other accessories or combinations thereof used in oil and gas production. These products are manufactured in various grades and in various sizes and lengths according to specifications provided by the American Petroleum Institute (API). [Example]

[0064] The present invention is illustrated by the following examples. It should be understood that the specific examples, materials, amounts, and procedures should be interpreted broadly in accordance with the scope and spirit of the present invention as described herein. Unless otherwise indicated, all parts and percentages are by weight, and all molecular weights are weight average molecular weights (Mw), as measured by methods known to those skilled in the art, preferably gel permeation chromatography (GPC) or size exclusion chromatography (GPC / SEC). Unless otherwise specified, all chemicals used are commercially available, for example, from Sigma-Aldrich (St. Louis, Missouri).

[0065] Test Method Unless otherwise indicated, the following test methods were utilized in the following examples.

[0066] Dry and wet erosion tests A modified version of ASTM G76 (Solid Particle Impingement Erosion Test) is used to test the erosion resistance of the coating systems described herein. A microabrasive or microblaster cabinet is used with an impact angle of 30 degrees and a test sample distance of approximately 2 inches (5.1 cm) from the blaster nozzle tip. Silica particles (500 g) are released at an air pressure setting of 28 psi and a desired velocity of 30 m / s to impact the surface of a coated test panel or an uncoated steel test panel (control). The coated sample is exposed to 500 g of silica sand or until the coating film erodes down to the substrate surface, whichever occurs first.

[0067] Erosion depth measurement To evaluate the depth of the erosion craters formed on the test samples, a contour measurement technique using a Keyence VHK-7000 series microscope was used. The microscope was focused on one edge of the test sample, collecting an image, and then moved to successive locations on the test sample to take more images. These images were then collated into a composite focus image of the sample, which could be used to measure the depth of the erosion crater (Zc) on the test sample relative to the steel control or blank (Zs). The erosion rate of the steel control (Es) and the erosion rate of the test sample (Ec) were calculated by dividing the crater depth by the weight of the silica sand that created the crater, as shown by the following equation: Erosion measurements were performed on coated panels in both the cured (dry) and exposed (wet) states. The use of this method is illustrated in Figures 1-3.

[0068]

number

[0069] Dynamic Mechanical Analysis (DMA) Testing To compare the various coating structures described herein as a function of temperature, free films were prepared and tested according to ASTM D5026-15 (Standard Test Method for Plastics: Dynamic Mechanical Properties: In Tension). Approximately 2.54 mm x 5 mm specimens were cut from the free films and tested by DMA using a standard commercially available analyzer, such as a TA Instruments Q850. Tests are conducted at 1 Hz with a pretension of 0.05 N to 0.1 N and a strain of 0.05% to 0.2%, while the films are heated from -20°C to the glass transition temperature (Tg) at a rate of 3°C per minute. This allows for the comparison of the film's elastic modulus, E', and the energy dissipation ratio, E'' / E', or tan δ, as a function of temperature.

[0070] DMA curves are used to compare the structures 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 indicated initially by a decrease in E', a peak in E'' in the middle, and a peak in the tan δ curve near the end. Above Tg, there may be a flat region in the E' curve, often referred to as the plateau modulus. This modulus value often indicates the crosslink density of the material. A comparable system with a higher E' plateau usually provides better barrier performance, provided it has good adhesion and flexibility. DMA test results for erosion-resistant coatings are shown in Figures 7 and 8.

[0071] In addition to dry air (dry erosion) testing, specimens from uncoated films are evaluated for wet erosion performance by DMA using a standard commercially available solids analyzer, such as the TA Instruments RSA-G2. Samples immersed in either deionized water or product water are evaluated using a film tension fixture and immersion apparatus, with testing conducted isothermally at 60°C (140°F) at a frequency of 1 Hz, 0.1% strain, and 0.1 N pretension. After 2 minutes of preconditioning in air, the test fluid (preheated to 60°C (140°F)) is added, and plasticization of the film can be observed through a decrease in modulus over a 30-minute test period. Immersion testing can be used to compare the effect of plasticization on mechanical properties. Significant changes can be predictive of even greater changes in the field, where longer exposure times and greater pressures are used. DMA test results for immersed erosion-resistant coatings are shown in Figure 6.

[0072] Coating hardness To measure the Martens hardness (a measure of the elasticity or plasticity of a coating) as described herein, a microindenter (e.g., a Fischerscope HM2000) is used on the coated test panel under dry ambient conditions of 23°C and 25% relative humidity, as described in EN ISO:14577-1 (Metallic Materials - Instrumented indentation test for hardness and materials parameters). The Vickers indenter is lowered to a force of 20 mN into the coating applied to the test panel, held for 5 seconds, and then removed. The contact area for indentation is 1-4 μm. 2 The maximum depth is about 3 μm. The results of the microindenter test of the erosion-resistant coating are shown in Figure 9.

[0073] Immersion Test To simulate field conditions, coated test panels are subjected to immersion tests in continuously agitated produced water at a temperature of approximately 60°C. The test panels are placed in a panel holder immersed in a mixing vessel containing an 80 / 20 volume mixture of produced water and kerosene (i.e., "produced water"), using separate samples for each time interval. After a predetermined period (14, 21, or 28 days), the samples are removed from the water, wiped dry, and then subjected to an erosion test.

[0074] Autoclave Test To evaluate post-exposure performance, metal test panels are coated with a one-component (1K) primer at a dry film thickness of 0.12 to 18 μm and then further coated with the coating described herein. The coating is allowed to cure, and the coated panels are evaluated for cure using differential scanning calorimetry (DSC). The coated panels are then placed in autoclave conditions at 60°C for 28 days at various pressures: 100 psi (7 days), 200 psi (14 days), 400 psi (21 days), and 800 psi (28 days). At 7-day intervals, the coated panels are inspected for appearance, adhesion, swelling, and blistering. ASTM D6677-18 (Standard Test Method for Evaluating Adhesion by Knife) is used to evaluate adhesion between the first and second coatings. A rating of 6 to 10 is considered acceptable for erosion-resistant coatings. If no appreciable changes are observed, the test panels are returned to the autoclave for an additional 7 days at higher pressures.

[0075] Example 1: Coating Formulation Various coating compositions shown in Table 1 were applied to metal test panels (1.5 in. x 3 in. x 1 / 8 in.) with a blast profile of 50-100 μm. The coated panels were then subjected to dry and wet erosion conditions and then evaluated for appearance and performance.

[0076] [Table 1]

[0077] Example 2: Evaluation of erosion performance The test formulations of Example 1 were evaluated for erosion resistance as described in the test methods above. To be an effective erosion coating, each formulation must adhere to the substrate without swelling or blistering upon exposure to produced water or other simulated field conditions. Additionally, an effective coating would pass the autoclave test described above.

[0078] The results of various performance evaluations are shown in Figure 4 (erosion rate against bare steel), Figure 5 (DMA comparison of immersion tests for coatings #3 and #5), Figure 6 (storage modulus after immersion test), Figure 7 (storage modulus as a function of temperature), Figure 8 (tan δ), and Figure 9 (hardness after autoclave test).

[0079] Example 3: Application of an Erosion Resistant Coating Metal test substrates were heated to 350°F (177°C) for 60 minutes, then the FBE coating was electrostatically applied to the substrate, followed immediately by a thermoplastic powder topcoat. The multi-coated substrates were cured in a 450°F (232°C) oven for 30-75 minutes and then allowed to cool to room temperature (23°C).

[0080] The complete disclosures of all patents, patent applications, and publications cited herein, as well as electronically available materials, are incorporated by reference. The foregoing "Description of Embodiments" and examples are given for clarity of understanding only. No unnecessary limitations should be understood therefrom. The invention is not limited to the exact details shown and described; variations obvious to those skilled in the art will be included within the invention defined by the claims. The invention illustratively disclosed herein may, in some embodiments, be practiced in the absence of any element not specifically disclosed herein.

Claims

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

2. 1. An erosion resistant coating system comprising: a first coating applied to a substrate, the first coating being corrosion resistant; a second coating applied over the first coating, the second coating comprising a thermoplastic component.

3. 1. A method of coating a substrate, comprising: Providing a substrate; Contacting at least one surface of the substrate with the coating system of any one of claims 1 to 2; and subjecting the substrate having the coating system applied thereto to conditions effective to form a cured coating on the substrate.

4. A coated article comprising: A substrate; and the coating system of any one of claims 1 to 3 applied to the substrate according to the method of any one of claims 1 to 3.

5. 5. The coating system, method, or article of any one of claims 1 to 4, optionally comprising a primer coating applied to the substrate prior to application of the first coating.

6. 6. The coating system, method, or article of any one of claims 1 to 5, optionally comprising a liquid phenolic primer coating applied to the substrate prior to application of the first coating.

7. 7. The coating system, method, or article of any one of claims 1 to 6, wherein the first coating applied to the substrate comprises a binder component selected from epoxy, polyester, polyurethane, polyamide, acrylic, polyvinyl chloride, nylon, fluoropolymer, silicone, other resin, or combinations thereof.

8. 8. The coating system, method, or article of any one of claims 1 to 7, wherein the first coating applied to the substrate comprises an epoxy resin binder component.

9. 9. The coating system, method, or article of any one of claims 1 to 8, wherein the first coating applied to the substrate is a fusion bonded epoxy (FBE) powder coating.

10. 10. The coating system, method, or article of any one of claims 1 to 9, wherein the first coating applied to the substrate is a thermoplastic composition.

11. The coating system, method, or article of any one of claims 1 to 10, wherein the first coating applied to the substrate is a thermosetting component.

12. 12. The coating system, method, or article of any one of claims 1 to 11, wherein the second coating applied over the first coating is a polyolefin modified with at least one α,β-unsaturated carboxylic acid or anhydride thereof.

13. 13. The coating system, method, or article of any one of claims 1 to 12, 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. 14. The coating system, method, or article of any one of claims 1 to 13, wherein the second coating applied over the first coating is a thermoplastic powder coating.

15. 15. The coating system, method, or article of any one of claims 1 to 14, optionally comprising a second coating applied over the first coating, the second coating being a thermoplastic liquid coating.

16. 16. The coating system, method, or article of any one of claims 1 to 15, wherein the second coating applied over the first coating is a monolayer extruded thermoplastic modified polyolefin film.

17. 17. The coating system, method, or article of any one of claims 1 to 16, wherein the second coating applied over the first coating is a multi-layer extruded thermoplastic film.

18. 18. The coating system, method, or article of any one of claims 1 to 17, wherein the second coating applied over the first coating is an extruded film of acid- or anhydride-modified polypropylene.

19. 19. The coating system, method, or article of any one of claims 1 to 18, wherein the second coating applied over the first coating is an extruded film of maleic anhydride modified polypropylene (PP-MA).

20. 20. The coating system, method, or article of any one of claims 1 to 19, wherein the second coating applied over the first coating is a maleic anhydride modified polypropylene (PP-MA) powder coating.

21. 21. The coating system, method, or article of any one of claims 1 to 20, wherein the second coating is an extruded thermoplastic film applied over the first coating to obtain a composite having a low modulus.

22. 22. The coating system, method, or article of any one of claims 1 to 21, wherein the second coating is an extruded thermoplastic film applied over the first coating to obtain a composite having a storage modulus (E') that remains stable over time upon exposure to product water.

23. 23. The coating system of any one of claims 1 to 22, wherein the coating system applied to a substrate exhibits erosion performance comparable to uncoated steel upon exposure to produced water.

24. 24. The coating system of any one of claims 1 to 23, wherein the coating system applied to a substrate exhibits erosion performance comparable to uncoated steel when exposed to produced water when tested according to ASTM G76.

25. 25. The coating system of any one of claims 1 to 24, wherein the coating system exhibits optimal immersion resistance in product water at 60°C for at least 28 days.

26. 26. The coating system of any one of claims 1 to 25, wherein the coating system exhibits optimal autoclave performance at 60°C and 800 psi for up to 28 days in a two-phase system when tested according to NACE TM0185.

27. 27. The coating system of any one of claims 1 to 26, wherein the first coating has a dry film thickness (DFT) of about 6 to 20 mils.

28. 28. The coating system of any one of claims 1 to 27, wherein the first coating has a dry film thickness (DFT) of about 8 to 16 mils.

29. 29. The coating system of any one of claims 1 to 28, wherein the first coating has a dry film thickness (DFT) of about 10 to 14 mils.

30. 30. The coating system of any one of claims 1 to 29, wherein the second coating has a dry film thickness of about 30 to 65 mils.

31. 31. The coating system of any one of claims 1 to 30, wherein the second coating has a dry film thickness of about 20 to 100 mils.

32. 32. The coating system of any one of claims 1 to 31, wherein the second coating has a dry film thickness of about 35 to 80 mils.

33. The coating system of any one of claims 1 to 32, wherein the first coating and the second coating together form a molecular composite coating system.

34. 34. The coating system of any one of claims 1 to 33, wherein the second coating is an extruded film derived from maleic anhydride modified polypropylene (PP-MA) having a particle size (D90) of 230 to 250 μm as determined by sieve analysis according to ASTM D1921-18.

35. 35. The coating system of any one of claims 1 to 34, wherein the second coating is an extruded film derived from maleic anhydride modified polypropylene (PP-MA) having a particle size (D90) of 390-410 μm as determined by laser diffraction.

36. 36. The coating system of any one of claims 1 to 35, wherein the first coating is a film derived from fusion bond epoxy (FBE) having a particle size (D90) of 110-130 μm as determined by laser diffraction.

37. 37. The coating system of any one of claims 1 to 36, wherein the first coating is a film derived from fusion bond epoxy (FBE) and having a porosity of about 1 to 4 when tested according to CSA Z2245.

20.

38. 38. The coating system of any one of claims 1 to 37, wherein the second coating is a film derived from maleic anhydride modified polypropylene (PP-MA) and having a porosity of about 1 to 4 when tested according to CSA Z2245.

20.

39. The coating system of any one of claims 1 to 38, wherein the system is applied to at least the inner diameter of a substrate, the substrate being at least one tubular item.

40. 40. The coating system of any one of claims 1 to 39, wherein the system is applied to at least the outer diameter of a substrate, the substrate being at least one tubular item.

41. 41. The coating system or method of any one of claims 1 to 40, wherein the first coating is applied to the substrate in a single application.

42. 42. The coating system or method of any one of claims 1 to 41, wherein the second coating is applied to the substrate in at least one application.

43. 43. The coating system or method of any one of claims 1 to 42, wherein the second coating is applied to the substrate in at least two applications.

44. 44. The coating system or method of any one of claims 1 to 43, wherein the substrate is heated to a temperature of at least 300°F (149°C) prior to applying the first coating composition.

45. 45. The coating system or method of any one of claims 1 to 44, wherein the substrate is heated to about 450F (232C) after the first and second coatings are applied.

46. 46. ​​The coating system or method of any one of claims 1 to 45, wherein the first coating composition is corrosion resistant as determined by CSA Z245.20.

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