Solid lubricants for Zn-Ni on tubular threaded elements

Abstract

The present invention relates to a tubular threaded element (1,2) for drilling and operating hydrocarbon wells, oil and gas transportation, hydrogen transportation or storage, carbon capture or geothermal energy. The tubular threaded element (1,2) comprises a metallic body (5) and at least one threaded end (3,4) including at least one threaded portion (14,15). The threaded end (3,4) comprises a multi-layer coating (10) on at least a portion of the surface of the threaded end (3,4), the multi-layer coating (10) comprising a first layer (11) comprising a solid coating comprising zinc-nickel electrodeposited on at least a portion of the surface of the threaded end (3,4), a second oxalate-type conversion layer (12) above the first layer (11), and a third layer (13) above the second layer (12) comprising a polyurethane or epoxy matrix carrying solid lubricant particles.

Description

[Technical Field]

[0001] The present invention relates to coated steel components or conduits used in the oil and gas, energy or storage sectors for applications such as well operation, hydrocarbon transport, hydrogen transport or storage, geothermal energy or carbon capture. [Background technology]

[0002] As used herein, the term "component" refers to any element, accessory, or conduit used to drill or operate a well. It has at least one connection or connector, and also a threaded end, and is intended to be assembled by threaded engagement with another component to form a threaded joint with the other component. The component may be, for example, a relatively long (especially about 10 meters long) tube or tubular threaded component, such as a pipe, or a tubular sleeve several tens of centimeters long, or accessories for these tubular components (suspension devices or "hangers," section changes or "crossovers," safety valves, connectors or "tool joints" or "subs" for drilling rods, etc.).

[0003] Tubular threaded components or elements are provided with threaded ends. These threaded ends are complementary, allowing for the connection of two male-threaded tubular elements ("pins") and two female-threaded tubular elements ("boxes"). Therefore, there are male and female threaded ends. These threaded ends, called premium or semi-premium threaded ends, generally include at least one abutment surface. The first abutment surface may be formed by two surfaces of the two threaded ends oriented substantially radially. These are configured to contact each other after the threaded ends are threaded together or during compressive stress. The abutment surface generally has a negative angle relative to the major axis of the connection. Intermediate abutment surfaces are also known in fittings with at least two thread stages. The threads, abutment surface, and sealing surface can form an assembly called a threaded end. A threaded end with a thread facing the pipe, i.e., a male threaded end, and a threaded end with a thread facing the inside of the pipe, i.e., a female threaded end, may be provided. The casing and finished tubular thread elements are made of steel and may be manufactured in accordance with, but not limited to, API Standard Specifications for Casing and Pipe 5CT or 5CRA. For example, the steel may be any of the following grades: L80, P110, or Q125.

[0004] The operating conditions of these tubular threaded elements generate different types of loads. These loads have been partially reduced by using films or greases, especially on vulnerable parts of these components, such as the threads, abutments, or metal-to-metal sealing surfaces. The induced stresses include those caused by maintenance, especially during storage. This necessitates the application of storage grease (different from the additional grease applied before commissioning). However, other solutions exist, such as the use of organic coatings. Thus, due to the weight of the several-meter-long pipes that are connected via the threaded end, and possibly even slight misalignment of the axes of the connected threaded elements, the screwing operation is generally carried out under high axial loads. This creates a risk of wear on the threads and / or metal-to-metal sealing surfaces. Therefore, the threaded areas and metal-to-metal sealing surfaces are typically coated with lubricants.

[0005] Additionally, tubular thread elements are often stored and used in harsh environments, such as "offshore" with salt spray or "onshore" with sand, dust, and / or other contaminants, requiring various types of corrosion protection coatings on threaded areas, clamping contacts, metal-to-metal sealing surfaces, seats, and abutments that are subject to stress during threading.

[0006] However, their use may not be a long-term solution in terms of environmental standards, as greases that comply with API RP5A3 (American Petroleum Institute) standards can be extruded from tubular components and released into the environment or wellbore, causing blockages that require specific cleaning operations.

[0007] An alternative to using grease is a dry and / or solid first layer or deposit. This metal deposit can be applied chemically or electrochemically. Depending on the nature of the deposit, it can provide corrosion resistance and lubrication properties to prevent wear on tubular threaded connections during threading. This can improve durability over applied grease, and its better solidity reduces contamination. However, these deposits can themselves corrode and spall during harsh environments, such as humid environments, or during aging, excessive stress on the connection, wellbore operation, and repeated threading and unthreading operations. Such corrosion or spalling is undesirable because it risks weakening the connection and loss of sealing due to the formation of leak paths associated with corrosion of the steel substrate of the tubular thread elements. For example, if a leak occurs during hydrocarbon well operation, the leak can have significant economic and environmental impacts.

[0008] European Patent Application No. 3286288 describes a solution in which a trivalent chromium passivation conversion layer is added on top of the solid deposits to separate them. However, the applicant has determined that this passivation layer does not assume a lubricating function and does not improve the lubricating properties of the upper layer. This lack of lubrication capability increases the risk of wear and streaking of the connection during screw-in / out tests, reducing efficiency as well as an undesirable increase in the screw-in torque. The increased screw-in torque means that the screw key's capacity is exceeded, making it impossible to screw in the connection and ensure its tightness.

[0009] "Striations" means grooves or scratches.

[0010] Deposition of a conversion layer is typically performed by inserting the target surface into a chemical bath that controls parameters such as deposition duration, chemical composition, and temperature. Summary of the Invention [Problem to be solved by the invention]

[0011] The present invention solves all of the above problems, and in particular proposes to improve and stabilize the underlayer or solid deposit while having a conversion process, chemistry, and easily controllable bath management that is compatible with current equipment. [Means for solving the problem]

[0012] According to one embodiment, the present invention provides a tubular threaded element for hydrocarbon well drilling and operation, oil and gas transportation, hydrogen transportation or storage, carbon capture, or geothermal energy. The tubular threaded element includes a metallic body and at least one threaded end portion including at least one threaded portion. The threaded end portion includes a multilayer coating on at least a portion of a surface of the threaded end portion. The multilayer coating includes a first layer including a solid coating comprising zinc-nickel electrodeposited on at least a portion of a surface of the threaded end portion, a second oxalate-type conversion layer over the first layer, and a third layer over the second layer including a polyurethane or epoxy matrix loaded with solid lubricant particles.

[0013] This feature provides the first solid deposit layer containing zinc-nickel with improved lubrication properties, protecting it from spalling, streaking, and wear. In fact, the second oxalate layer acts as a solid lubricant for the first layer. This allows the Zn-Ni solid deposit layer to have a more stable and durable wear coefficient. The resulting wear coefficient can be less than 0.2. In fact, the applicant has confirmed that a value greater than 0.2 poses a risk of wear. The second oxalate layer also provides a chemically or mechanically insulating barrier to the Zn-Ni sublayer or the first solid deposit layer. The second oxalate layer amplifies the effect of the third lubricant layer. The latter provides an additional lubrication effect, thereby improving the threadability of the connection.

[0014] Surprisingly, when the conversion layer is of the oxalate type, it exhibits a uniform appearance around the circumference of the connection, regardless of the flow or temperature in the bath, making it easier to identify coating problems. The oxalate layer also improves the overall coating adhesion in wet conditions and after aging, thus better protecting performance even after long-term storage.

[0015] Additionally, the use of oxalic acid is less restrictive from the perspective of current regulations and is not classified as CMR, i.e., not carcinogenic, mutagenic, or reproductively toxic.

[0016] By "coverage problem" is meant a lack of coverage of the sublayer or first deposited layer, i.e., areas of the first layer that are not covered by the oxalate layer and are visible to the naked eye.

[0017] According to one embodiment, the tubular screw element has a second oxalate conversion layer that may include nickel oxalate and / or zinc oxalate.

[0018] This feature allows nickel and zinc oxalates to delay metal-to-metal contact and store some of the dissipated energy released during screwing of the connection. Surprisingly, the addition of nickel oxalate can improve the corrosion resistance of the conversion layer.

[0019] According to one embodiment, the tubular screw element has a second layer that may include 10% to 20% carbon, 35% to 50% zinc, 35% to 45% oxygen, and 0% to 35% nickel.

[0020] Surprisingly, the applicant has found that this feature allows the oxalate layer to improve the material's resistance to multi-layer coatings.

[0021] According to one embodiment, the layer weight of the second layer is 0.1 g / m 2 ~20g / m 2 The range may be:

[0022] This characteristic has revealed that durability is proportional to the layer weight, and the greater the layer weight, the higher the durability.

[0023] However, once the layer weight exceeds a certain threshold, cohesive failure of the resulting oxalate layer becomes problematic: the layer breaks on its own when subjected to external stress. This results in the risk of delamination or flaking of the oxalate layer, which can lead to the delamination of the third layer.

[0024] According to one embodiment, the surface mass of the second layer is 0.5 g / m 2 ~10g / m 2 The applicant has determined that the range of 10 g / m 2 Until now, we have determined that this offers a better compromise between good durability and reduced risk of cohesive failure.

[0025] According to one embodiment, the porosity of the second layer may be in the range of 5% to 35%.

[0026] According to one embodiment, the porosity of the second layer may be in the range of 10% to 25%.

[0027] This porosity allows the upper layer to be fixed into the voids in the oxalate layer, improving the retention and coating of the upper layer. According to one embodiment, the thickness of the second layer may be in the range of 0.5 μm to 30 μm.

[0028] According to one embodiment, the thickness of the second layer may be in the range of 1 μm to 20 μm.

[0029] This feature improves the resistance of the material in multilayer coatings. Layer thicknesses exceeding 30 μm can cause problems with cohesive failure. Layers less than 0.5 μm thick are insufficient and can cause problems with insufficient lubrication.

[0030] According to one embodiment, the second layer may comprise a microcrack polyhedron type texture with edges between 1 μm and 30 μm wide.

[0031] "Microcrack polyhedron" refers to a three-dimensional geometric shape with planar polygonal faces grouped into segments called edges. The number of faces and edges can be any number, and edge lengths can range from 0.5 μm to 30 μm. The layer may have randomly distributed microcracks. The crack widths can range from 0.05 μm to 1 μm.

[0032] Due to this feature, the microcrack polyhedron type texture provides improved retention and adhesion to the overlying layer.

[0033] Also, according to one embodiment, the present invention relates to a method for manufacturing a tubular screw element, the method comprising: Electrodepositing a zinc-nickel layer on the metal surface of the threaded end; an oxalate conversion step by immersion; coating with a lubricating layer comprising a polyurethane or epoxy matrix loaded with solid lubricant particles; Includes:

[0034] This feature allows the coating to be applied without appreciably altering the zinc-nickel layer.

[0035] "Dipping" refers to the technique of treating the surface by immersion in a bath of oxalic acid.

[0036] According to one embodiment, the oxalate conversion step may be carried out at a temperature ranging from 25°C to 90°C.

[0037] This feature allows the use of the same tools as for passivation, reducing setup and material costs.

[0038] According to one embodiment, the oxalate conversion step may involve the use of oxalic acid, the concentration of which may range from 1 g / L to 75 g / L.

[0039] This feature allows for easier management and control of the layer weight of the oxalate layer. In fact, the closer to 75 g / L the more rapid the surface conversion reaction becomes.

[0040] According to one embodiment, the oxalate conversion step can include the use of oxalic acid in association with an additive selected from the elements nitrate, chloride, thiocyanate, or thiosulfate, or a combination of several additives.

[0041] This feature allows the additive to accelerate the surface conversion reaction, thereby achieving the desired layer weight properties more quickly.

[0042] The process for depositing the oxalate layer can be carried out for a time ranging from 30 seconds to 15 minutes. The time will affect the value of the layer weight, which is proportional to the immersion time.

[0043] Below 30 seconds, the bed weight is insufficient. Above 15 minutes, there is no significant change in the bed weight value. [Brief explanation of the drawings]

[0044] Other objects, details, features and advantages of the present invention will become apparent from the following description of various embodiments of the present invention with reference to the accompanying drawings. [Figure 1] 1 is a partial cross-sectional view showing a schematic representation of a joint resulting from the assembly of two tubular internal threads and an internally threaded element according to the invention; FIG. [Figure 2] 1 is a cross-sectional view showing a schematic representation of a portion of a multilayer coating according to the present invention. [Figure 3] 1 is a graph showing the change in threading torque at each end of the thread for various types of coatings applied to a tubular threaded element for various connections that include either an oxalating or passivating treatment. [Figure 4]4 is a graph showing the change in threading torque at each end of the thread for various types of coatings applied to a tubular thread element for one of the connections different from that of FIG. 3, including either an oxalating treatment or a passivation treatment. [Figure 5] 1 is a graph showing the number of steps required in the BOWDEN test, which number depends on the layer weight for different types of conversion, in particular until an abrasion factor for the layer weight reaches 0.2. [Figure 6] 1 is a SEM (scanning electron microscope) image of a cross-section of a multilayer coating according to the present invention. [Figure 7] 1 is a SEM (scanning electron microscope) image showing a cross section of a multilayer coating according to the prior art. [Figure 8] 1 is a 5000x magnified SEM (scanning electron microscope) image of the surface of an oxalate conversion layer according to the present invention viewed from above. [Figure 9] 1 is a 20,000x magnified SEM (scanning electron microscope) image of the surface of an oxalate conversion layer according to the present invention, viewed from above. DETAILED DESCRIPTION OF THE INVENTION

[0045] In the following description, the terms "longitudinal," "lateral," "longitudinal," "front," "rear," "left," and "right" are defined with reference to a common orthogonal frame of reference, as shown in the figures, which includes a horizontal longitudinal axis X, running from left to right in the cross-sectional view.

[0046] Also, in this specification and the appended claims, the terms "external" or "internal," as well as "axial" and "radial," are used in accordance with the definitions set forth herein to designate elements of a tubular threaded joint. The longitudinal axis X determines the "axial" direction. The "radial" direction is perpendicular to the longitudinal axis X.

[0047] Figure 1 shows a joint or connection along a longitudinal axis X of a first tubular externally threaded element (1) according to the invention, comprising a metallic body (5) and an externally threaded end (3), which comprises a male abutment surface (6), a male sealing surface (8), and an externally threaded portion (14). In the figure, the first tubular externally threaded element (1) is assembled with a second tubular threaded element (2) according to the invention, comprising a metallic body (5) and an internally threaded end (4), which comprises a female abutment surface (7), a female sealing surface (9), and an internally threaded portion (15).

[0048] Each of the male threaded end (3) and the female threaded end (4) is comprised of a metal substrate (20) and a multi-layer coating (10) on the metal substrate (20).

[0049] Although the tubular screw elements (1, 2) are shown in a threaded state, the invention does not exclude the possibility that they may be shown in an integrated, unthreaded state.

[0050] The multi-layer coating (10) may be provided on one or the other of the male threaded end (3) and the female threaded end (4), or on both simultaneously. In particular, the multi-layer coating (10) may be provided on the male abutment surface (6) or the female abutment surface (7), on the male sealing surface (8) or the female sealing surface (9), on the male threaded portion (14) or the female threaded portion (15), or on some or all of these surfaces. In Figure 1, the multi-layer coating (10) is provided on the male threaded end (3).

[0051] 2 shows a cross section of a multi-layer coating (10) on a metal substrate (20) of a male threaded end (3). However, the coating (10) may be present on a metal substrate of a female threaded end as well. Therefore, all treatments relating to the multi-layer coating (10) on the male threaded end (3) apply equally to the multi-layer coating (10) on the female threaded end.

[0052] In particular, the figure shows a multi-layer coating (10) comprising a first solid coating layer (11) comprising zinc-nickel electrodeposited on the surface of the male threaded end (3), i.e., on the metal substrate (20) that makes up the male threaded end (3).

[0053] The multi-layer coating (10) comprises a first layer (11) over which a second oxalate conversion layer (12) is formed.

[0054] The second conversion layer (12) of oxalate type can contain nickel oxalate and / or zinc oxalate (not shown), these two elements being derived from the oxalate layer by reaction of oxalic acid with the zinc-nickel layer.

[0055] Finally, a third lubricating layer (13) comprising a polyurethane or epoxy matrix loaded with solid lubricant particles is deposited over the second layer (12), the solid lubricant particles being selected from, but not limited to, PTFE, talc, chromium oxide, and alumina.

[0056] Advantageously, the first solid deposit layer (11) containing zinc-nickel provides improved lubrication properties, protecting it from spalling, streaking, and wear. In fact, the second oxalate layer acts as a solid lubricant on the first layer. This provides the first solid deposit layer (11) containing Zn-Ni with a much more stable and durable coefficient of friction. This coefficient of friction is less than 0.2. In fact, above 0.2, there is a risk of wear.

[0057] In fact, the applicant has demonstrated by comparison that this stability and durability is not found in passivation layers (see Figures 3 and 4). The second oxalate layer (12) also provides a chemically and mechanically insulating barrier effect to the Zn-Ni-containing sublayer or first solid-deposit layer (11). The second oxalate layer (12) amplifies the effect provided by the third layer (13), which provides an additional lubricating effect in combination with the lubricating effect provided by the second layer (12), improving the threadability of the connection (see Figure 3).

[0058] Additionally, the use of oxalic acid is less restrictive from the perspective of current regulations and is not classified as CMR, meaning it is not carcinogenic, mutagenic, or reproductively toxic.

[0059] Advantageously, the second oxalate layer (12) comprises nickel oxalate and zinc oxalate, which allows to delay metal-to-metal contact and to store some of the dissipated energy released during the screwing of the connection.

[0060] In fact, when the coating (10) is crushed by the action of screwing the threaded end, the functional surfaces of the end come into contact with very high contact pressure. The second layer (12), which is subject to stress and pressure, crushes before the first solid layer (11). This protects the first layer (11) and improves the overall durability of the coating (10). Surprisingly, it was also found that the addition of nickel oxalate can improve the corrosion resistance of the conversion layer.

[0061] 3 shows in a comparative manner the change in the threading torque at the end of threading for various types of coatings of tubular threaded elements according to the invention, with a passivation-type layer or an oxalated-type layer, of the prior art. "At the end of threading" refers to the moment when the two fasteners, the male and female tubular threaded elements, come into contact during the threading / unthreading (M&B) cycle.

[0062] One method used to verify proper assembly of a connection and determine when it is fully threaded is to monitor the torque applied by a collet relative to the number of revolutions. A "collet" is a large-capacity, self-locking wrench used to grip the male and female parts of a connection and apply the tightening / loosening torque. By connecting the collet's load cell and an electronic tachometer to a computer, a graph can be plotted with torque on the vertical axis and number of revolutions on the horizontal axis. By tallying up the end-of-thread times, a new graph can be created, as shown in Figure 3.

[0063] Also shown in Figure 3 is a dashed line at approximately 70,000 Nm representing the PLT, or maximum wrench capacity. As this curve approaches or reaches its maximum wrench capacity, there is a high probability of connection wear, limiting the maximum number of possible tightening / loosening or screwing / unscrewing operations (M&B).

[0064] The connections used in Figure 3, whether coated or not, are all identical, i.e., the connections correspond to VAM® SLIJ-II type tubular thread elements. These types of pipes were tested and verified according to the API RP 5C5:2017 CAL II standard.

[0065] Each curve represents a coating comprising a first layer of electrodeposited zinc-nickel, a second passivated or oxalated conversion layer according to the present invention, and a third lubricant layer, so that only the nature of the second conversion layer varies from one curve to another.

[0066] Curves 1 and 2 show coatings with a chromium III passivation layer, the presence of these two curves corresponding to two screw-in tests with the same coating.

[0067] Curves 3 and 4 show coatings with oxalate layers where iron nitrate was used as an accelerator during layer deposition. The presence of these two curves corresponds to two screw-in tests with the same coating.

[0068] Curves 5 and 6 show coatings with an oxalate layer without the use of an accelerator, the presence of these two curves representing two screw-in tests with the same coating.

[0069] 3 shows that all of the curves showing passivation, i.e., curves 1 and 2, increased in torque with each screwing / unscrewing operation, approaching dangerously close to PLT as the screwing / unscrewing rotations increased. The opposite trend was observed for the curves showing oxalation, i.e., curves 3, 4, 5, and 6. In fact, these curves were substantially flat, resulting in a stable torque as the screwing / unscrewing operation progressed. While curves 3, 4, 5, and 6 show stability for up to five screwing / unscrewing rotations, the applicant has been able to demonstrate that this stability continues for up to 15 screwing / unscrewing rotations when the second layer (12) is an oxalated layer according to the present invention.

[0070] Additionally, the coatings of curves 1 and 2 showed wear and striations at the roots, crests and seats of the threads as the screwing / unscrewing rotations progressed, i.e. damage to the electrodeposited zinc-nickel layer.

[0071] With respect to the oxalate type coating, the Applicant has discovered that no wear occurs, no damage occurs to the first zinc-nickel layer, and a tribofilm is formed that provides an insulating barrier effect to the entire multi-layer coating.

[0072] The results of the comparative analysis are not limited to the above but are valid for any type of tubing in the oil and gas, energy or storage sectors, for example for well development, hydrocarbon transport, hydrogen transport or storage, geothermal energy or carbon capture applications.

[0073] FIG. 4, like FIG. 3, compares the change in threading torque at the end of threading for different types of coatings, using the same method as in FIG. 3, for another type of connection, namely VAM® SLIJ-III.

[0074] Curves 1, 2, and 3 correspond to thread ends coated with a coating comprising a second passivation-type layer. The coating was applied to the entire thread end, i.e., the thread or threaded portion, the abutment face, and the sealing seat. There are three curves because they correspond to the number of tests carried out with the same coating. Curves 4 and 5 correspond to thread ends with a multilayer coating according to the invention comprising a second oxalate-type layer.

[0075] The comparative analysis and results were similar to those shown in FIG.

[0076] Curves 1, 2, and 3 show that the torque increased from the second screwing / unscrewing. Curve 1 shows that the corresponding joint could not be screwed / unscrewing for the fifth time due to wear. Curves 4 and 5 show that the torque remained stable for all screwing / unscrewing.

[0077] Applicant has demonstrated that the stability and reliability of the oxalation treatment according to the present invention, as well as its superior passivation properties, are not limited to VAM® SLIJ-II, but are transferable from one type of joint to another.

[0078] FIG. 5 is a graph showing the number of steps required to reach a coefficient of friction of 0.2 in the BOWDEN test, i.e., the number of strokes of the steel ball, depending on the layer weight of the second conversion layer, depending on the type of coating.

[0079] Each test sample was coated with a similar coating comprising at least one first Zn-Ni layer and a lubricant layer, with the variation between samples corresponding to the presence and / or nature of a second layer.

[0080] Comparing the three types of coatings, the coating without a conversion layer, i.e., without passivation or oxalation, has a layer weight of 0 g / m 2 In the coatings with a second passivation type layer, the layer weight was 0.1 g / m2 in both cases (shown as squares on the graph). 2 and 0.15 g / m 2 (shown as a circle on the graph). In fact, in the case of passivation treatment, 2 Finally, for multilayer coatings according to the present invention having a second oxalate-type layer (shown as triangles on the graph), numerous tests were carried out with coatings of various types of layer weights.

[0081] When two rough moving parts are in contact, wear mechanisms can cause the material to shrink and, as a result of plastic deformation, produce debris. The value of the friction coefficient depends on the mechanical properties of the surface, such as its composition and structure, roughness, plasticity, ductility, and resistance to shear stress. For coatings on connections, the value of the friction coefficient should be less than 0.2. Above 0.2, there is a risk of wear occurring.

[0082] To evaluate the lubricity (friction coefficient) of the coating surface, a commercially available Bowden abrasion tester (manufactured by Shinko Engineering) was used. In the Bowden abrasion tester, a steel ball (100CR6) was moved back and forth linearly over the coating formed on the steel plate while a load was applied to the steel ball. The friction coefficient was measured from the friction force and pressure load at that time.

[0083] The steel balls used in the Bowden abrasion test were commercially available steel balls (100CR6) (manufactured by Amatsuji Steel Ball Mfg. Co., Ltd.) with an outer diameter of 10 mm that had been degreased in advance.

[0084] A steel ball was placed against the evaluation coating and moved with a pressing load of 300N.

[0085] From Figure 5, it can be seen that the coating without a conversion layer reaches the critical friction threshold of 0.2 before reaching 150 steps.

[0086] The passivated coating provided substantially greater lubricity than the unconverted layer, reaching a critical threshold of 0.2 coefficient of friction in approximately 200 steps.

[0087] The oxalated coating provided superior lubricity to the two coatings mentioned above, reaching a critical threshold of 0.2 for the friction coefficient in the range of 400 to 600 steps depending on the layer weight. Therefore, the oxalated coating provided a more stable and durable friction coefficient for the Zn-Ni solid deposit layer.

[0088] Indeed, the applicant has determined that the oxalate layer specifically improves the plastic deformation of Zn-Ni at its surface, even under high contact pressure, improving the stability of the system before atomic dislocations, grain rotations, and the appearance of large block flaking and large scale defects.

[0089] Even at lower layer weights, the oxalate layer was found to form a longer-lasting lubricating film and improve lubrication efficiency, either chemically or physically.

[0090] According to a variant of the invention, the layer weight of the second layer (12) is 0.1 g / m 2 ~20g / m 2 The range is.

[0091] According to another variant of the invention, the layer weight of the second layer (12) is 0.5 g / m 2 ~10g / m 2 The range is.

[0092] Advantageously, it has been found that durability is proportional to layer weight, with higher layer weights resulting in greater durability.

[0093] However, once the layer weight exceeds a certain threshold, cohesive failure of the resulting oxalate layer becomes an issue. The layer will break on its own when subjected to external stress. This results in a risk of delamination or flaking of the oxalate layer, which can lead to the delamination of the third lubricating layer. The applicant has developed a 10 g / m 2 It was determined that up to 1000 MPa offered a better compromise between good durability and reduced risk of cohesive failure.

[0094] FIG. 6 is a SEM (Scanning Electron Microscope) image of a cross-section of a multi-layer coating (10) according to the present invention on a metal substrate (20) at the end of an external thread (3).

[0095] The multilayer coating (10) comprises a first layer (11) of a solid coating comprising electrodeposited zinc-nickel. The coating also comprises an oxalate conversion layer 12. The third lubricant layer, comprising a polyurethane or epoxy matrix loaded with solid lubricant particles, cannot be observed in situ; therefore, a plastic coating resin (22) was used to prepare the sample for metallographic observation. Note that this resin (22) is useful only for obtaining the image shown in Figure 6 and does not form part of the present invention.

[0096] FIG. 7 is a SEM (Scanning Electron Microscope) image of a cross-section of a multi-layer coating (100) with a passivation layer (102) according to the prior art on a metal substrate (120) of a male threaded end (103).

[0097] The multilayer coating (100) comprises a first layer (101) of a solid coating comprising electrodeposited zinc-nickel. The coating also comprises a passivated conversion layer (102). The third lubricant layer, comprising a polyurethane or epoxy matrix loaded with solid lubricant particles, cannot be observed in situ; a plastic coating resin (22) was used to prepare the metallographic sample. This resin (22) is only useful for obtaining the image shown in Figure 7.

[0098] Observations in Figure 6 indicate a textured oxalate layer with a thickness of approximately 5 μm, however, other observations suggest that the oxalate layer may range from 0.5 μm to 30 μm, preferably from 1 μm to 20 μm.

[0099] Comparing with the image of FIG. 7, the second passivation type conversion layer was not observed since it was less than 100 nm.

[0100] This difference in observation is important in that it ensures a minimum thickness for oxalation while still maintaining visibility. In comparison, this visibility was not observed with the passivation shown in Figure 7. This thickness has advantages, such as improving the resistance of the material. Indeed, on the one hand, thicknesses above a certain threshold (especially 30 μm) can cause problems with cohesive failure. On the other hand, layers of 0.5 μm or less than 500 nm are insufficient and inevitably cause problems with insufficient lubrication.

[0101] Cohesive failure is an undesirable effect that can reduce or eliminate the effectiveness of the second layer, leaving the first zinc-nickel layer vulnerable to environmental and induced stresses.

[0102] The crack (24) and other cracks observed in the zinc-nickel layer shown in Figures 6 and 7 are due to sample preparation for metallographic purposes.

[0103] Advantageously, applicants have determined that the thickness of the second oxalate layer has an insulating barrier type effect on the first solid zinc-nickel layer.

[0104] 6 shows the porosity of the second oxalate layer 12. The porosity of the second layer 12 was in the range of 5% to 35%.

[0105] According to a variant of the invention, the porosity of the second layer (12) may be in the range of 10% to 25%.

[0106] "Second layer porosity" refers to the voids between the bases of the crystals, which may cover the voids with their height. It is also called open porosity when there are cracks that run directly between the zinc-nickel layer and the third layer, which contains a polyurethane or epoxy matrix loaded with solid lubricant particles.

[0107] Advantageously, the porosity allows the upper layer to be mechanically fixed into the voids of the oxalate layer, improving the retention of the upper layer of the multi-layer coating.

[0108] This porosity was not observed in the second passivated conversion layer according to the prior art, as compared to Figure 7. In fact, applicants determined that the passivated layer was too thin to allow for any appreciable porosity.

[0109] FIG. 8 is a 5000x magnified SEM (scanning electron microscope) image of the surface of the oxalate conversion layer (12) viewed from above.

[0110] In particular, it can be seen that the surface of the layer is textured by microcrack polyhedrons (30).

[0111] "Microcracked polyhedron" refers to a three-dimensional geometric shape with planar polygonal faces grouped into segments called edges. The number of faces and edges can be any number, and edge lengths can range from 0.5 μm to 30 μm. The layer may have randomly distributed microcracks. The crack widths can range from 0.05 μm to 1 μm. This feature allows the microcracked polyhedron type texture to provide improved retention and adhesion to the overlying layer.

[0112] According to a variant of the invention, the second layer (12) can be produced using an accelerator, which has the effect of promoting homogenization of the oxalation and obtaining a thinner, denser layer.

[0113] FIG. 9 is a SEM (scanning electron microscope) image magnified 20,000 times showing the surface of the oxalate conversion layer according to the present invention as viewed from above.

[0114] The contents of FIG. 8 are also applicable to FIG. 9 and are valid.

Claims

1. A tubular threaded element (1, 2) for drilling and operating hydrocarbon wells, oil and gas transportation, hydrogen transportation or storage, carbon capture or geothermal energy, comprising: a metallic body (5); and at least one threaded end (3, 4) including at least one threaded portion (14, 15), the threaded end (3, 4) comprising a multi-layer coating (10) on at least a portion of a surface of the threaded end (3, 4), the multi-layer coating (10) comprising: a first layer (11) comprising a solid coating comprising zinc-nickel electrodeposited on at least a portion of a surface of the threaded end (3, 4); a second oxalate-type conversion layer (12) over the first layer (11); and a third layer (13) over the second oxalate-type conversion layer (12) comprising a polyurethane or epoxy matrix carrying solid lubricant particles. The layer weight per unit area of ​​the second oxalate conversion layer (12) is 0.1 g / m ２ ~20g / m ２ is in the range of The tubular screw element (1, 2) is characterized in that the thickness of the second oxalate conversion layer (12) is in the range of 0.5 μm to 30 μm.

2. 2. The tubular thread element (1, 2) according to claim 1, characterized in that the second oxalate conversion layer (12) comprises nickel oxalate and / or zinc oxalate.

3. The layer weight per unit area of ​​the second oxalate conversion layer (12) is 0.5 g / m ２ ~10g / m ２ 2. The tubular thread element (1, 2) according to claim 1, characterized in that the thread length is in the range of

4. 2. The tubular thread element (1, 2) according to claim 1, characterized in that the porosity of the second oxalate conversion layer (12) is in the range of 5% to 35%.

5. A tubular thread element (1, 2) according to claim 4, characterized in that the porosity of the second oxalate conversion layer (12) is in the range of 10% to 25%.

6. 6. The tubular thread element (1, 2) according to claim 5, characterized in that the thickness of the second oxalate conversion layer (12) is in the range of 1 μm to 20 μm.

7. 2. The tubular thread element (1, 2) according to claim 1, characterized in that the second oxalate conversion layer (12) comprises a microcrack polyhedron type texture with edges having a width of 1 μm to 30 μm.

8. 2. A tubular threaded element (1, 2) according to claim 1, characterized in that the threaded end (3, 4) further comprises at least one abutment surface (6, 7) and at least one sealing surface (8, 9), and the multilayer coating (10) covers the at least one abutment surface (6, 7) and / or the at least one sealing surface (8, 9).

9. A method for manufacturing a tubular thread element (1, 2) according to any one of claims 1 to 8, comprising: electrodepositing a zinc-nickel layer on the metal surface of the threaded ends (3, 4); an oxalate conversion step; coating with a layer comprising a polyurethane or epoxy matrix loaded with solid lubricant particles; A method comprising:

10. 10. The method of claim 9, wherein the oxalate conversion step is carried out at a temperature ranging from 25°C to 90°C.

11. 10. The method of claim 9, wherein the oxalic acid conversion step comprises the use of oxalic acid, the concentration of which ranges from 1 g / L to 75 g / L.

12. 10. The method of claim 9, wherein the oxalate conversion step comprises the use of oxalic acid in association with an additive, or a combination of additives, selected from the elements nitrate, chloride, thiocyanate, and thiosulfate.

Images