RU2626827C1 - Antiscuff coating for threaded joint of pump-compressor and casing tubes and method of its production - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: antiscuff coating is made from the composition, containing the following components (in weight percent): the organic binder of 30%-60%, the solid lubricant of 30%-60%, the corrosion inhibitor of 6%-15%, the levelling agent of 0.01%-0.1%, the wetting agent 0.01%-0.1% and in addition the mixture of solvents. The organic binder is the liquid polyamide-imide resin with the solids content of 38-42%. The solid lubricant is any substance from the molybdenum disulphide and tungsten disulphide or the combination of molybdenum disulphide or tungsten disulfide with polytetrafluoroethylene. Preferably, the solid lubrication and the corrosion inhibitor are the surface-modified with the silane bonding agent. The antiscuff coating is obtained by spraying the coating on the surface of the threaded joint of pump-compressor and casing tubes, treated with phosphate; thus avoiding the environmental contamination with the heavy metal powder, contained in the threaded grease.

EFFECT: production of coatings that have good antiscuff and anticorrosive properties.

7 cl, 8 dwg, 16 ex

Description

Technical field

The present invention relates to the technical field of surface treatment, in particular, to an anti-seize coating for threaded connections of tubing and casing, as well as to a method for its production.

State of the art

Tubing and casing are vital products for the exploration and production of oil and gas. Casing pipes are connected by threaded connections to obtain a casing string to support the walls of the well; tubing is connected by threaded connections to obtain a tubing string to form a channel for oil production.

The connection of tubing and casing consists of an internal thread and an external thread, which are screwed and unscrewed by a screwing force and a screwing force during use. A threaded joint is equivalent to a friction pair. From the microscopic point of view, when the surfaces of the internal and external threads are in contact with each other, the actual contact area of the two contacting bodies is limited to only a few microprotrusions of the surfaces to be connected; high contact pressure causes plastic deformation of microprotrusions, forming local welding points; meanwhile, due to the same internal and external thread material and high mutual solubility, when the surfaces of the internal thread and the external thread slide relative to each other, adhesive failure occurs due to metal migration at the point of contact of the threads of the tubing and casing pipes, namely, scoring in connecting tubing and casing.

Since the absence of seizure during the connection of tubing and tubing during repeated screwing and unscrewing is one of the important operational characteristics, in order to solve the problem of seizure in threaded joints, the existing technology is used to treat the surface of the threaded joint (phosphating, plating of copper- tin, etc.) and the threaded joint are coated with threaded lubricants when tightened to ensure that there is no scuff in the joint. However, threaded lubricants contain powders of heavy metals, mainly lead and zinc, which can cause serious environmental pollution and cannot meet the requirements of environmental legislation. At present, the use of threaded lubricants during geological exploration and development of oil and gas fields in the North Sea is limited. In order to guarantee the extreme pressure characteristics of the tubing and casing during their use and compliance with environmental legislation, one of the main ways to solve the problem is to develop environmentally friendly tubing and casing joints without threading.

Chinese Patent Application No. 20100056281.2 describes a pipe joint with coated coatings and tapered threads. This application describes a threaded connection for pipes, including an internal part with an external thread and an external part with an internal thread; while the external thread of the inner part is made in such a way that it corresponds to the internal thread of the outer part; the shape of the internal thread and external thread usually has a dovetail profile with a mortgage and supporting sides of the thread and flat troughs and peaks of the thread profile; the thickness of the internal thread on the external part increases in one direction, and the thickness of the external thread on the internal part increases in the other direction, so the troughs of the thread profile, the tips of the thread profile and the side surfaces of the thread profile are shifted and form seals that prevent fluid from flowing between these seals. The threaded connection further includes a fluoroplastic-based coating applied to specific areas of the internal thread and external thread, and a resin-based coating located in the areas of the internal thread and external thread that are not coated with a fluoroplastic; wherein the fluoroplastic-based coating and the resin-based coating are such that they form a layer of substantially uniform thickness over the entire surface of the internal thread and the external thread. This application describes two types of coatings with different ingredients in different parts of the tapered surface of the thread: one of them is a fluoroplastic-based coating, and the other is a resin-based coating.

Chinese Patent Application No. 20100056638.7 describes a wedge-shaped thread with a solid lubricant coating. The pipe connection described in this application includes an internal part having an external wedge-shaped thread configured to connect to an external part having a corresponding internal wedge-shaped thread and a solid lubricating coating applied to at least one of the internal and external wedge-shaped threads; wherein the solid lubricating coating comprises a first uniform coating layer of a corrosion inhibiting dry coating made of an epoxy resin containing zinc particles and a second uniform coating layer of a dry lubricant covering the first uniform layer. This application describes a two-layer structure, namely one dry corrosion inhibiting layer made of an epoxy resin containing zinc particles and another layer of a mixture of molybdenum disulfide and another solid lubricant in an inorganic binder. These two described layers can also be combined in a hard coating.

Chinese Patent Application No. 20070042743.3 describes a lubricating coating composition for pipe joints. The lubricating coating composition described in this application contains one or more alkaline lubricants selected from alkali metal sulfonate, alkali metal salicylate, alkali metal phenolate and alkali metal carboxylate, and this composition has a biodegradability (BOD) of at least 20 %, when measured after 28 days in sea water.

Chinese Patent Application No. 02804104.6 describes a threaded connection for steel pipes with increased resistance to abrasion and corrosion. This application describes a porous zinc or zinc alloy base prepared by a blast plating process and a solid lubricating film (consisting of a lubricant powder in an organic or inorganic binder) or a liquid lubricating film that does not contain heavy metal powders (e.g. liquid film, mainly based on a salt of a strongly alkaline metal and an organic acid, for example, a sulfonate of a strongly alkaline metal). After coating, corrosion of the compound can be prevented, and it can be used repeatedly.

Chinese Patent Application No. 200710018769.6 describes an anti-seize and self-lubricating thread coating and method for preparing it. This application describes a two-component self-lubricating coating consisting of Component A and Component B. Component A contains the following starting materials (in mass percent): film-forming substances: 40-90%, solid lubricant: 5-60%, additives: 0-10 %, solvent: 0-50%, pigment: 0-10%, filler: 0-10%; Component B contains the following starting materials (in mass percent): curing agent: 50-100%, solvent: 0-50%; the mass ratio of Component A to Component B is from about 1: 0.1 to 1: 5. Curing of coatings after their application can occur naturally at room temperature, and the curing time can be shortened by heating accordingly.

Chinese Patent Application No. 20060044680.0 describes a threaded joint with high and low friction coatings. The high friction coating mentioned in this application consists of an epoxy resin or an esterified epoxy resin containing MoS ₂ , graphite and / or boron nitride; low friction coating consists of fluoroplastics.

The content of the invention

The aim of the present invention is to provide an anti-seize coating for threaded connections of tubing and casing, as well as a method for its production. By spraying the coating of the present invention onto a phosphate-treated tubing and casing joint surface, an anti-seize coating is obtained for joining the tubing and casing tubing without applying a thread lubricant, thereby solving the problem of environmental pollution with heavy metal powders included in the thread grease.

To achieve the above objectives, the present invention includes the following technical program:

Anti-seize coating for threaded connection of tubing and casing, including (in percent):

organic binder: 30% -60%

solid lubricant: 30% -60%

corrosion inhibitor: 6% -15%

leveling agent: 0.01% -0.1%

wetting agent: 0.01% -0.1%

and a mixture of solvents, which is additionally added in an amount 3-4 times the total mass of solids of the organic binder, solid lubricant, corrosion inhibitor, leveling agent and wetting agent;

wherein said organic binder is a liquid polyamidimide resin having a solids content of 38-42% by weight .;

said solid lubricant is polytetrafluoroethylene and molybdenum disulfide, or polytetrafluoroethylene and tungsten disulfide, or molybdenum disulfide, or tungsten disulfide; while the content of polytetrafluoroethylene in the solid lubricant is 0-30% by mass., and the content of molybdenum disulfide or tungsten disulfide in said solid lubricant is 70-100% by mass .;

said corrosion inhibitor is titanium dioxide, or calcium stearate, or both of these substances;

said leveling agent is fluorocarbon modified polyacrylic acids; said wetting agent is polyether silicone copolymers;

said solvent mixture includes (in mass percent): 40-50% N-methylpyrrolidone, 30-40% dimethylformamide and 10-20% ethyl acetate.

In addition, molybdenum disulfide and tungsten disulfide included in the solid lubricant are surface modified molybdenum disulfide powders and surface modified tungsten disulfide powders; moreover, the modifier is selected from a silane coupling agent based on aminosilanes or a silane coupling agent based on isocyanatesilanes.

The titanium dioxide in said corrosion inhibitor is surface modified titanium dioxide powders; moreover, the modifier is selected from a silane coupling agent based on aminosilanes or a silane coupling agent based on isocyanatesilanes.

Said selected modifier is selected from aminopropyltriethoxysilane or methacryloxypropyltrimethoxysilane or isocyanatepropyltriethoxysilane.

Furthermore, said modifying treatment in the present invention is carried out using a wet modifying process by the following steps. Firstly, a silane coupling agent based on aminosilanes, isocyanatesilanes is hydrolyzed by using ethanol having a concentration of 75-95% for 10-15 minutes and at pH 3-5; powders of molybdenum disulfide, or tungsten disulfide, or titanium dioxide are dispersed in anhydrous ethanol by ultrasonic dispersion; the amount of anhydrous ethanol is 10-15 times greater than the mass of powders of molybdenum disulfide, or tungsten disulfide, or titanium dioxide. Anhydrous ethanol is then heated to 60-65 ° C with stirring, followed by the addition of a hydrolyzed silane coupling agent based on aminosilanes or isocyanatesilanes at a rate of 0.05-0.1 ml / min, while the amount of silane coupling agent based on aminosilanes or isocyanatesilanes is 10 -20% by weight of powders of molybdenum disulfide, or tungsten disulfide, or titanium dioxide; mixing is carried out for 6-8 hours at 60-65 ° C. Finally, the mixture resulting from the above process is filtered under vacuum; the filter cake is washed 3-5 times with deionized water and anhydrous ethanol, and then dried under vacuum for 10-12 hours at 100-120 ° C, and then crushed in a ball mill for use.

A preferred leveling agent described is EFKA3772 manufactured by EFKA Company, The Netherlands; type: 3772. EFKA3772 is a fluorocarbon-modified polyacrylate with good leveling and anti-shrink properties, with adequate neutralization with ammonia after dissolution in water, and good compatibility as a mechanical polymer in all polymer systems.

A preferred wetting agent described is WET245 manufactured by TEGO Company, Germany; type: WET245. WET245 is a copolymer of polyether and silicone, as well as a substrate wetting agent containing 100% active substance and having good overlap, good fluidity, anti-shrink and anti-seize (increase adhesion) properties, some anti-foaming effect.

In addition, the solid lubricant and corrosion inhibitor mentioned in the present invention are powder particles with a particle size of 0.1-0.5 microns; leveling agent, wetting agent and solvent mixture are liquids.

The method of producing an anti-seize coating for connecting tubing and casing pipes described in the present invention includes the steps of spraying the coating material onto a phosphorized thread surface and the sealing surface of the connection of the tubing and casing pipes, placing them together in heating equipment, heating to a temperature of 250- 280 ° C and holding for 0.1-0.3 hours to obtain an anti-seize coating with a thickness of 8 to 15 microns.

Scheme of the coating composition of the present invention:

The role of the organic binder is to combine solid particles in a solid lubricant and corrosion inhibitor with some adhesion to the thread surface of the threaded joint of the tubing and casing.

The performance of the solid lubricant film bound by an organic binder mainly depends on the type of resin included in the matrix and on the composition of the solid lubricant. Particles of solid lubricant are connected to the metal base by means of a binder; the binder used in anti-seize coatings must have high abrasion resistance and a low friction coefficient, and also have good mechanical strength and adhesion characteristics to ensure an adequate coating life. Commonly used organic binders are epoxy resins, polyphenylene sulfide, polyetheretherketone, polyimide and polyamide, polyamide imide resin, etc. Various organic binders have different mechanical properties, the degree of shrinkage during curing, stability, manufacturability, tribological characteristics, etc. Polyamidimide is a new type of engineering plastics, which is a type of polymer with a regular alternating arrangement of imide rings and amide bonds; the performance of this polyimide polymer is superior to that of conventional polyimide. Polyamidimide is resistant to high temperatures and radiation, has a wide operating temperature range from -195 ° C to 230 ° C; it has excellent dimensional stability and creep resistance; its elasticity, abrasion resistance, alkali resistance, manufacturability and adhesion are equivalent to or superior to the corresponding characteristics of polyimide. In the present invention, polyamidimide is selected as an organic binder for the operating conditions of a threaded connection of tubing and casing.

Solid lubrication acts as a lubricating phase. When choosing the lubricating phase, attention should be paid to the reasonable correspondence of solid lubricant and organic binder to increase chemical affinity and increase adhesion. There are many types of solid lubricating phase; commonly used solid lubricant material mainly refers to materials with a layered structure, having low shear strength and easily sticking to the surface of the base.

Consider, for example, molybdenum disulfide; it has a layered structure of the hexagonal system; the layers are connected to each other by weak molecular forces; the material is easily split into layers, and thus has good lubricity. The good lubricity of molybdenum disulfide is determined by its crystalline structure. Because the bonds between the sulfur and molybdenum atoms in each molecular layer are very strong, but the bonds between the sulfur and molybdenum atoms between the molecules are very weak, a plane with a low shear is obtained; when there is very little shear between the molecules, the material is easily separated along the molecular layer to form a slip plane. For example, there are 800 molecular layers and 799 slip planes in the film of a surface of 0.5 nm thick molybdenum disulfide. These numerous slip planes lead to the fact that the direct contact of two metal surfaces, initially sliding relative to each other, is transformed into a slip of the molecular layers of molybdenum disulfide relative to each other, thereby reducing the friction coefficient and reducing abrasive wear.

MoS ₂ has a low coefficient of friction, usually 0.03-0.15, which is less than the coefficient of friction of graphite; under good conditions, the coefficient of friction can reach 0.017. The friction coefficient of MoS ₂ decreases with increasing load; the greater the load, the lower the coefficient of friction. In addition, due to the layered structure of MoS ₂ , the sulfur and molybdenum atoms are firmly bonded, so that its compressive strength exceeds that for other lubricants. The bond strength of sulfur and metal atoms is also very high, so that MoS ₂ can form strong adsorption bonds on the surface of the metal, with the formation of a layer of a very strong film; an extremely thin layer of MoS ₂ film can perform very well as a lubricant, and MoS ₂ is currently the most widely used solid lubricant.

The role of the solid lubricant is to form a layer of the transition film on the surface of the thread during the process of tightening the joint to separate the microprotrusions of the external thread and the internal thread at the contact points, so that cold welding cannot occur; this can prevent scoring when a relative displacement of the external thread and the internal thread occurs in the case of cold welding on the surface of the thread, and thereby ensure the performance of extreme pressure functions.

The role of surface modification MoS ₂ . After fine grinding of solid particles, especially powders of inorganic substances, the force field acting on the atoms located on the surface of the powder particles and the force field acting on the atoms inside the crystal are significantly different; the force applied to the internal atoms arises due to the symmetric valence bonds of the surrounding atoms and the long-range Van der Waals forces from more distant atoms; the applied forces are symmetrical, and the valence bonds of the atom are saturated; as a result, there is a tendency to form bonds with atoms located from the outside, and reunification with the formation of secondary particles with poor dispersion easily occurs, which seriously affects the efficiency of their use. Molybdenum disulfide (MoS ₂ ) has a layered structure. One layer of Mo atoms is located between two layers of S atoms with the formation of an elementary layer comprising three planar layers of S-Mo-S; between the layers there are only weak van der Waals forces. MoS _{2 is} easy to split into layers, so it has good characteristics as a solid lubricant. The surface energy of such split surfaces is low and they are hydrophilic, which makes them difficult to disperse in the organic phase and apply in the coating composition, and also affects the stability of the coatings. Therefore, in the present invention, before MoS _{2 was} added to the coatings, MoS ₂ was treated to modify the surface in order to improve its interfacial compatibility with polymers and prevent reunion, which affects its dispersion.

In the case where directly the MoS ₂ particles are dispersed in the resins to form a coating, MoS ₂ will precipitate during application over a period of time. After treatment with MoS ₂ to modify the surface, bonds will form on the surface of MoS ₂ ; these bonds can interact with bonds in the resin, preventing the deposition of MoS ₂ .

The role of the corrosion inhibitor is to prevent corrosion of the threaded joint of the tubing and casing in the working environment.

The role of additives is mainly to improve the manufacturability of the coating and the performance of the coating itself. The choice of additives is related to the selected coating composition and a number of factors, for example, such as the surface condition of solid lubricant particles, surface condition of the workpiece, coating viscosity, etc. The content of additives is very small; the content of all additives is only 0.01-1% of the total mass. A certain content of additives in coatings can prevent coating defects, such as bubbles in coatings, poor coating alignment, flocculation, deposition, etc. When choosing additives, they mainly take into account high efficiency, low negative impact, high cost of execution, compliance with environmental legislation, etc. Also pay attention to the compatibility of additives with the device.

Compared with existing patents, the present invention has the following features:

The binder of the present invention is an organic binder; coating structure is single layer; The corrosion inhibitor component in the coating is titanium dioxide, or calcium stearate, or both.

The surface modification treatment was carried out for molybdenum disulfide or tungsten disulfide in the solid lubricant of the present invention, as well as for titanium dioxide in a corrosion inhibitor.

Description of drawings

FIG. 1 and FIG. 2 are photographs of the surface morphology of the threaded joint of the tubing of the present invention after 11 screwing and unscrewing of this threaded joint during testing.

FIG. 3 and FIG. 4 are photographs of the surface morphology of the threaded joint of the casing after 4 times screwing and unscrewing of this threaded joint during testing.

FIG. 5 is a photograph of the morphology of a sample of the internal thread of a compound before testing for corrosion resistance when sprayed with saline.

FIG. 6 is a photograph of the morphology of the sample after testing for corrosion resistance by spraying with saline for 100 hours.

FIG. 7 is a photograph of the surface morphology of a sample of internal thread before being tested for atmospheric conditions.

FIG. 8 is a photograph of the morphology of a sample after being tested for atmospheric conditions for 6 months.

Embodiments of the invention

Further, the present invention is described using the following examples and drawings.

Example 1

The composition of the applied composition (mass percent):

49.8% polyamidimide, 10% polytetrafluoroethylene, 30% modified molybdenum disulfide, 5% modified titanium dioxide, 5% calcium stearate, 0.1% leveling agent, 0.1% wetting agent; the amount of solvent mixture is 3 times the mass of the above components.

Coating process: pressure in the atomizer 0.25 MPa; exposure at 280 ° C in an oven for 0.3 hours.

Results: after the processing described above, the adhesion strength level 1 between the coating and the connection of the tubing P110 was obtained; after 11-fold screwing and unscrewing, there are no scoring; after testing for corrosion resistance when spraying with neutral saline for 100 hours, no foci of corrosion were found.

Example 2

30.89% polyamidimide; 7% polytetrafluoroethylene; 49% modified molybdenum disulfide; 10% modified titanium dioxide; 3% calcium stearate; 0.01% leveling agent; 0.1% wetting agent; the amount of the solvent mixture is 4 times the mass of the above components.

Coating process: pressure in the atomizer 0.25 MPa; exposure at 280 ° C in an oven for 0.1 hour.

Results: after the processing described above, the adhesion strength level 1 between the coating and the connection of the tubing P110 was obtained; after 11-fold screwing and unscrewing, there are no scoring; after testing for corrosion resistance when spraying with neutral saline for 100 hours, no foci of corrosion were found.

Example 3

57.89% polyamidimide; 4% polytetrafluoroethylene; 32% modified molybdenum disulfide; 5% modified titanium dioxide; 1% calcium stearate; 0.1% leveling agent; 0.01% wetting agent; the amount of solvent mixture is 3.5 times the mass of the above components.

Coating process: pressure in the atomizer 0.25 MPa; exposure at 250 ° C in an oven for 0.1 hour.

Results: after the processing described above, the adhesion strength level 1 between the coating and the BG110SS tubing connection was obtained; after 11-fold screwing and unscrewing, there are no scoring; after testing for corrosion resistance when spraying with neutral saline for 100 hours, no foci of corrosion were found.

Example 4

31.98% polyamidimide; 1% polytetrafluoroethylene; 59% modified molybdenum disulfide; 5% modified titanium dioxide; 3% calcium stearate; 0.01% leveling agent; 0.01% wetting agent; the amount of the solvent mixture is 4 times the mass of the above components.

Coating process: pressure in the atomizer 0.25 MPa; exposure at 250 ° C in an oven for 0.3 hours.

Results: after the processing described above, a bond strength level 1 was obtained between the coating and the BG90H casing joint; after 4 times screwing and unscrewing, there are no scoring; after testing for corrosion resistance when spraying with neutral saline for 100 hours, no foci of corrosion were found.

Example 5

44.89% polyamidimide; 5% polytetrafluoroethylene; 35% modified molybdenum disulfide; 10% modified titanium dioxide; 5% calcium stearate; 0.1% leveling agent; 0.01% wetting agent; the amount of solvent mixture is 3.5 times the mass of the above components.

Coating process: pressure in the atomizer 0.25 MPa; exposure at 250 ° C in an oven for 0.2 hours.

Results: after the processing described above, the adhesion strength level 1 between the coating and the BG110SS tubing connection was obtained; after 11-fold screwing and unscrewing, there are no scoring; after testing for corrosion resistance when spraying with neutral saline for 100 hours, no foci of corrosion were found.

Example 6

59.89% polyamidimide; 5% polytetrafluoroethylene; 25% modified molybdenum disulfide; 7% modified titanium dioxide; 3% calcium stearate; 0.01% leveling agent; 0.1% wetting agent; the amount of the solvent mixture is 4 times the mass of the above components.

Coating process: pressure in the atomizer 0.25 MPa; exposure at 280 ° C in an oven for 0.1 hour.

Results: after the processing described above, the adhesion strength level 1 between the coating and the connection of the tubing P110 was obtained; after 11-fold screwing and unscrewing, there are no scoring; after testing for corrosion resistance when spraying with neutral saline for 100 hours, no foci of corrosion were found.

Example 7

30.89% polyamidimide; 57% modified molybdenum disulfide; 9% modified titanium dioxide; 3% calcium stearate; 0.01% leveling agent; 0.1% wetting agent; the amount of the solvent mixture is 4 times the mass of the above components.

Coating process: pressure in the atomizer 0.25 MPa; exposure at 280 ° C in an oven for 0.1 hour.

Results: after the processing described above, the adhesion strength level 1 between the coating and the connection of the tubing P110 was obtained; after 11-fold screwing and unscrewing, there are no scoring; after testing for corrosion resistance when spraying with neutral saline for 100 hours, no foci of corrosion were found.

Example 8

59.89% polyamidimide; 30% modified molybdenum disulfide; 7% modified titanium dioxide; 3% calcium stearate; 0.1% leveling agent; 0.01% wetting agent; the amount of solvent mixture is 3 times the mass of the above components.

Coating process: pressure in the atomizer 0.25 MPa; exposure at 250 ° C in an oven for 0.3 hours.

Results: after the processing described above, the adhesion strength level 1 between the coating and the connection of the tubing P110 was obtained; after 11-fold screwing and unscrewing, there are no scoring; after testing for corrosion resistance when spraying with neutral saline for 100 hours, no foci of corrosion were found.

Example 9

30.89% polyamidimide; 57% modified tungsten disulfide; 9% modified titanium dioxide; 3% calcium stearate; 0.01% leveling agent; 0.1% wetting agent; the amount of the solvent mixture is 4 times the mass of the above components.

Coating process: pressure in the atomizer 0.25 MPa; exposure at 280 ° C in an oven for 0.1 hour.

Results: after the processing described above, the adhesion strength level 1 between the coating and the connection of the tubing P110 was obtained; after 11-fold screwing and unscrewing, there are no scoring; after testing for corrosion resistance when spraying with neutral saline for 100 hours, no foci of corrosion were found.

Example 10

59.89% polyamidimide; 30% modified tungsten disulfide; 7% modified titanium dioxide; 3% calcium stearate; 0.1% leveling agent; 0.01% wetting agent; the amount of solvent mixture is 3 times the mass of the above components.

Coating process: pressure in the atomizer 0.25 MPa; exposure at 250 ° C in an oven for 0.1 hour.

Results: after the processing described above, the adhesion strength level 1 between the coating and the connection of the tubing P110 was obtained; after 11-fold screwing and unscrewing, there are no scoring; after testing for corrosion resistance when spraying with neutral saline for 100 hours, no foci of corrosion were found.

Example 11

31.98% polyamidimide; 1% polytetrafluoroethylene; 59% modified tungsten disulfide; 5% modified titanium dioxide; 3% calcium stearate; 0.01% leveling agent; 0.01% wetting agent; the amount of the solvent mixture is 4 times the mass of the above components.

Coating process: pressure in the atomizer 0.25 MPa; exposure at 280 ° C in an oven for 0.1 hour.

Results: after the processing described above, the adhesion strength level 1 between the coating and the connection of the tubing P110 was obtained; after 11-fold screwing and unscrewing, there are no scoring; after testing for corrosion resistance when spraying with neutral saline for 100 hours, no foci of corrosion were found.

Example 12

59.89% polyamidimide; 5% polytetrafluoroethylene; 25% modified tungsten disulfide; 7% modified titanium dioxide; 3% calcium stearate; 0.01% leveling agent; 0.1% wetting agent; the amount of the solvent mixture is 4 times the mass of the above components.

Coating process: pressure in the atomizer 0.25 MPa; exposure at 250 ° C in an oven for 0.3 hours.

Results: after the processing described above, the adhesion strength level 1 between the coating and the connection of the tubing P110 was obtained; after 11-fold screwing and unscrewing, there are no scoring; after testing for corrosion resistance when spraying with neutral saline for 100 hours, no foci of corrosion were found.

Example 13

57.89% polyamidimide; 4% polytetrafluoroethylene; 32% modified molybdenum disulfide; 6% modified titanium dioxide; 0.1% leveling agent; 0.01% wetting agent; the amount of solvent mixture is 3.5 times the mass of the above components.

Coating process: pressure in the atomizer 0.25 MPa; exposure at 250 ° C in an oven for 0.2 hours.

Results: after the processing described above, the adhesion strength level 1 between the coating and the BG110SS tubing connection was obtained; after 11-fold screwing and unscrewing, there are no scoring; after testing for corrosion resistance when spraying with neutral saline for 100 hours, no foci of corrosion were found.

Example 14

57.89% polyamidimide; 5% polytetrafluoroethylene; 25% modified molybdenum disulfide; 6% calcium stearate; 0.1% leveling agent; 0.01% wetting agent; the amount of solvent mixture is 3.5 times the mass of the above components.

Coating process: pressure in the atomizer 0.25 MPa; exposure at 250 ° C in an oven for 0.2 hours.

Results: after the processing described above, the adhesion strength level 1 between the coating and the BG110SS tubing connection was obtained; after 11-fold screwing and unscrewing, there are no scoring; after testing for corrosion resistance when spraying with neutral saline for 100 hours, no foci of corrosion were found.

Example 15

30.89% polyamidimide; 7% polytetrafluoroethylene; 49% modified molybdenum disulfide; 13% modified titanium dioxide; 0.01% leveling agent; 0.1% wetting agent; the amount of solvent mixture is 4 times the mass of the above components.

Coating process: pressure in the atomizer 0.25 MPa; exposure at 280 ° C in an oven for 0.1 hour.

Results: after the processing described above, the adhesion strength level 1 between the coating and the connection of the tubing P110 was obtained; after 11-fold screwing and unscrewing, there are no scoring; after testing for corrosion resistance when spraying with neutral saline for 100 hours, no foci of corrosion were found.

Example 16

30.89% polyamidimide; 7% polytetrafluoroethylene; 49% modified molybdenum disulfide; 13% calcium stearate; 0.01% leveling agent; 0.1% wetting agent; the amount of the solvent mixture is 4 times the mass of the above components.

Coating process: pressure in the atomizer 0.25 MPa; exposure at 280 ° C in an oven for 0.1 hour.

Results: after the processing described above, the adhesion strength level 1 between the coating and the connection of the tubing P110 was obtained; after 11-fold screwing and unscrewing, there are no scoring; after testing for corrosion resistance when spraying with neutral saline for 100 hours, no foci of corrosion were found.

The surface of the connections of the tubing and casing was carried out using the extreme pressure coating of the present invention, and then full-scale tests of extreme pressure physical characteristics were carried out when screwing and unscrewing the test object; the number of tests must comply with the requirements of ISO 13679, namely, seizure should not be observed after 9-fold screwing and unscrewing of the tubing and after 2-fold screwing and unscrewing the casing. The test results show that the adhesion strength of the coating and the base metal is high, and the coating is resistant to peeling when heated; the number of screwing and unscrewing of tubing and casing without scoring reached 11 and 4, respectively, which corresponds to the extreme pressure requirements for threaded joints of tubing and casing. The physical morphology of the surface of the external thread of the connection of the tubing (without any processing after machining) and the internal thread after phosphating, coated with the present invention, after 11-fold screwing and unscrewing, is shown in FIG. 1 and FIG. 2. The physical morphology of the surface of the external thread of the casing joint (without any treatment after machining) and the internal thread after phosphating with the coating of the present invention after 4-fold screwing and unscrewing is shown in FIG. 3 and FIG. four.

The use of the coating of the present invention for surface treatment of the connection of tubing, followed by the use of a protective ring for 10-fold screwing and testing for corrosion resistance when spraying with saline for 100 hours, without any foci of corrosion on the coating, as shown in FIG. 5 and FIG. 6, ensures compliance with the anti-corrosion requirements for threaded connections of tubing and casing pipes during transportation and storage.

The use of the coating of the present invention for surface treatment of tubing joints and subsequent exposure to atmospheric conditions in the Baoshan region of Shanghai for 6 months did not reveal any signs of corrosion, as shown in FIG. 7 and FIG. 8.

Based on the foregoing, the results obtained when testing extreme pressure characteristics using screwing and unscrewing the threaded joints of tubing and casing pipes show that the adhesion strength of the coating to the base metal is high and the coating has good extreme pressure characteristics that can meet the requirements for tightening and unscrewing tubing and casing without the use of thread lubricants that pollute the environment .

Claims (23)

1. Anti-seize coating for threaded connections of tubing and casing, including (in mass percent): organic binder: 30-60%, solid lubricant: 30-60%, corrosion inhibitor: 6-15%, leveling agent: 0.01-0.1%, wetting agent: 0.01-0.1%, and a mixture of solvents, which is additionally added in an amount 3-4 times the total mass of solids of an organic binder, solid lubricant, corrosion inhibitor, leveling agent and wetting agent, said organic binder is a liquid polyamidimide resin having a solids content of 38-42% by weight .; said solid lubricant is polytetrafluoroethylene and molybdenum disulfide, or polytetrafluoroethylene and tungsten disulfide, or molybdenum disulfide, or tungsten disulfide, the molybdenum disulfide and tungsten disulfide in said solid lubricant are surface-modified molybdenum disulfide powders, surface-modified the modifier is selected from a silane coupling agent based on aminosilanes or a silane coupling agent based on isoc anatsilanov; the content of polytetrafluoroethylene in the specified solid lubricant is 0-30% by mass., and the content of molybdenum disulfide or tungsten disulfide in the specified solid lubricant is 70-100% by mass .; said corrosion inhibitor is titanium dioxide, or calcium stearate, or both, the titanium dioxide in said corrosion inhibitor is surface-modified titanium dioxide powders, wherein the modifier is selected from an aminosilane-based silane coupling agent or a silane coupling agent based on isocyanatesilanes; said leveling agent is fluorocarbon modified polyacrylic acids; said wetting agent is polyether silicone copolymers; said solvent mixture includes (in mass percent): 40-50% N-methylpyrrolidone, 30-40% dimethylformamide and 10-20% ethyl acetate. 2. An anti-seize coating for the threaded connection of tubing and casing according to claim 1, wherein said modifier is selected from aminopropyltriethoxysilane (APTES), methacryloxypropyltrimethoxysilane or isocyanatepropyltriethoxysilane. 3. Anti-seize coating for threaded connection of tubing and casing according to claim 1, characterized in that said modifying treatment is carried out using a wet modifying process through the following steps: firstly, a silane coupling agent based on aminosilanes or isocyanatesilanes is hydrolyzed by using ethanol having a concentration of 75-95% for 10-15 minutes and at pH 3-5; powders of molybdenum disulfide, or tungsten disulfide, or titanium dioxide are dispersed in anhydrous ethanol by ultrasonic dispersion; the amount of anhydrous ethanol is 10-15 times greater than the mass of powders of molybdenum disulfide, or tungsten disulfide, or titanium dioxide; then the anhydrous ethanol is heated to 60-65 ° C with stirring, followed by the addition of a hydrolyzed silane coupling agent based on aminosilanes or isocyanatesilanes at a rate of 0.05-0.1 ml / min, while the amount of silane coupling agent based on aminosilanes or isocyanatesilanes 10-20% by weight of molybdenum disulfide or tungsten disulfide or titanium dioxide powders; mixing is carried out for 6-8 hours at a temperature of 60-65 ° C; finally, after the mixture obtained by the above process was filtered under vacuum, the filter cake was washed 3-5 times with deionized water and anhydrous ethanol, and then dried under vacuum for 10-12 hours at a temperature of 100-120 ° C, after which crushed in a ball mill for use. 4. Anti-seize coating for threaded connection of tubing and casing pipes according to claim 1, characterized in that said leveling agent is EFKA3772 manufactured by EFKA (Netherlands), Type 3772. 5. Anti-seize coating for threaded connection of tubing and casing pipes according to claim 1, characterized in that said wetting agent is WET245 manufactured by TEGO (Germany), Type WET245. 6. Anti-seize coating for the threaded connection of tubing and casing pipes according to claim 1, characterized in that said solid lubricants and corrosion inhibitors are powder particles with a particle size of 0.1-0.5 microns, and said leveling agent, said the wetting agent and said solvent mixture are liquids. 7. A method of producing an anti-seize coating for a threaded connection of tubing and casing according to claim 1, comprising the following steps: spraying the coating material onto a phosphorized thread surface and a sealing surface of said tubing and casing joint; their joint placement in heating equipment, heating to a temperature of 250-280 ° C and holding for 0.1-0.3 hours to obtain an anti-seize coating with a thickness of 8 to 15 microns.

Images