OA17435A - Assembly for producing a galling-resistant threaded tubular connection. - Google Patents

Abstract

The invention concerns an assembly for the production of a threaded connection, comprising a first and a second tubular component each with an axis of revolution (10) and each provided at one of their ends (1,2) with a threaded zone (3; 4) produced on the outer or inner peripheral surface of the component depending on whether the threaded end is male or female in type, said ends (1,2) being capable of cooperating by makeup and ending in a terminal surface (7, 8), at least one first contact surface being provided on one of the ends (1, 2) and at least one second contact surface being provided on the corresponding end (1, 2), such that the first and second contact surfaces come into contact during makeup of the ends (1, 2), characterized in that the first and second contact surfaces are respectively each coated with a first and a second dry thermoplastic film the matrices of which are constituted by one or more thermoplastic polymers, only one of the first and second dry thermoplastic films further comprising a liquid amorphous thermoplastic resin with a dynamic viscosity in the range 2000 to 40000 mPa.s at 25°C.

Description

ASSEMBLY FOR PRODUCING A GALLING-RESISTANT THREADED

TUBULAR CONNECTION [001] The présent invention relates to threaded connections for drilling and/or operating hydrocarbon wells, and more precisely to optimizing the overall performance of a connection in terms of galling résistance and gas seal by means of a synergistic association of solid thermoplastic coatings at least one of which comprises a liquid amorphous thermoplastic resin.

[002] The term “threaded connections” means any assembly constituted by two éléments with a substantially tubular shape that are capable of being assembled together by makeup, with a view in particular to constitute either a stem that can be used to drill a hydrocarbon well or a work over riser or a riser for operating a well of this type, or a casing or tubing string used in operating a well.

[003] Each tubular component comprises an end portion provided with a male threaded zone or a female threaded zone intended to be made up with a corresponding end portion of an analogous element. Once connected in this manner, the éléments compose what is termed a connection.

[004] Such threaded tubular components of a connection are connected under defined loads in order to satisfy the requirements for an interférence fit and seal imposed by the service conditions. Further, it should be known that the threaded tubular components may be required to undergo several makeup-breakout cycles, in particular when in service.

[005] The conditions for use of such threaded tubular components give rise to different types of loads, which makes it necessary to use films on the sensitive portions of such components such as the threaded zones, abutting zones or sealing surfaces.

[006] Thus, makeup operations are generally carried out under a high axial load, for example because of the weight of a tube several métrés in length to be connected via the threaded connection, possibly aggravated by a slight misalignment of the axis of the threaded éléments to be connected. This induces risks of poor shouldering of the abutments (poor pressurization of the sealing surfaces) and this induces the risk of galling at the threaded zones and/or at the metal/metal sealing surfaces. The threadejr

zones and the metal/metal sealing surfaces are therefore routinely coated with lubricants.

[007] In current designs, it is necessary to select a coefficient of friction such that a torque on shoulder résistance value which is at least equal to a threshold value is obtained. In this manner, it is possible to avoid reducing the value of the optimum makeup torque defined for this type of connection and for the référencé API grease and in extreme cases of avoiding no longer being able to guarantee the function of the abutment.

[008] Some approaches hâve consisted of differentiatîng the coefficient of friction as a function of the loading zone by preferentially applying a PTFE bonded coating to the threadings (longitudinal movement loading zone) without coating the axial or abutment loading zone in order to locally generate a high coefficient of friction (see, for example, document US20090033087).

[009] Other approaches hâve consisted of focussing on a shouldering torque of less than 70% of the value of the optimum clamping torque using essentially viscoplastîc coatings (see, for example, the documents W02008/125740, W02009/072486). However, an essentially waxy thermoplastic coating runs the risk of plastification of the abutment before it reaches the optimum clamping torque, in particular for thîn connections with small dimensions of the T&C (threaded and coupled) type or connections known as “high torque” connections.

[010] For the skilled person, it is possible to increase the shear forces during the phase known as friction plastification of the makeup abutment (i.e. at the end of the tightening phase) by an elastic effect using thermoplastic materials with rheo-resistant behaviour in a matrix with a solid consîstency (see, for example, the document WO2010043316). However, the résistance to shear causes excessive heating, which has a tendency to modify the rheological viscoplastîc properties of the matrix in the longitudinal movement loading zone and to affect the film effect which allows a large number of makeup/breakout operations.

[011] In order to overcome the problem, the skilled person elected to adjust the elastic effect by surface migration or by impregnating a friction modifier into a solid thermoplastic matrix with a high softening point with the aîm of reducing the value of the shouldering torque without affecting the torque on shoulder résistance as a function of

the loading zone and of providing a résistance to galling, even in the case of a rupture of the film beyond a loading ceiling (see, for example, the documents WO2010114168 and WO2012049194). Although the effect occurs in the initial zone and at the end of tightening, the lubricant film is easily extruded in an abundance of flakes due to a combination of factors attributed to the choice of thermoplastic polymers which constitute the matrix. The softening point or melting point is preferably in the range 80°C to 320°C and is much higher than a température corresponding to those to which the constituents are exposed during storage or use in order to prevent the polymers from picking up dust and other contaminants due to their tacky nature. In addition, polymers such as a copolyamide of acid dimers which hâve a rubber-like thermodynamic behavîour make the matrix hîghly cohesive, opposing the force of adhesion.

[012] Alternatively, patent document W02009057754 and more recently patent document WO2012060472 hâve proposed the production of a thin layer of a lubricating film with a pasty or waxy consistency (known as a “semi-dry” film) comprising materials which provide a résistance to friction which dépends on the contact pressure. These solutions use a rosin dérivative or “tackîfying” solid resin with a softening point in the range 60°C to 200°C or a calcium fluoride, for example. The braking principle is, however, greatly limited, attributed to the fact that the highly viscous matrix contributes to limiting sliding at the metal-metal interface and as a resuit, increases the friction. In addition, the thin film is not in the solid state, which is a disadvantage during transport, storage and use (risk of contamination).

[013] Based on this observation, the présent invention is based on a synergistic effect of the required properties, by applying two solid thermoplastic coatings having a differential coefficient of friction and thermodynamic behavîour facing each other and irrespectively of whether it is on the male or female end of the connection. The présent invention thus proposes obtaining a torque on shoulder résistance which is 100% or more of the reference value of API 5A3 grease, conserving the lubricant film for as long as possible between the surfaces in contact in order to ensure optimal lubrication performance.

[014] In particular, the présent invention pertains to an assembly for the production of a threaded connection, comprising a first and a second tubular component each with

ι

an axis of révolution and each provided at one of their ends with a threaded zone produced on the outer or inner peripheral surface of the component depending on whether the threaded end is male or female in type, said ends being capable of cooperating by makeup and ending in a terminal surface, at least one first contact surface being provided on one of the ends and at least one second contact surface being provided on the corresponding end, such that the first and second contact surfaces corne into contact during makeup of the ends, characterized in that the first and second contact surfaces may respectively each be coated with a first and a second dry thermoplastic film the matrices of which may be constituted by one or more thermoplastic polymers, only one of the first and second dry thermoplastic films further comprising a liquid amorphous thermoplastic resin with a dynamic viscosity in the range 2000 to 40000 mPa.s at 25°C.

[015] Optional, complementary or substitutional characteristics are set out below.

[016] The first and second contact surfaces may be a portion of the threaded zones.

[017] The first and second contact surfaces may be sealing surfaces provided on the circumferential surface of the ends of the first and second tubular components.

[018] The first and second contact surfaces may be abutment surfaces provided on the terminal surfaces of said ends.

[019] The thermoplastic polymer or polymers constituting the matrix of the first and second dry films may hâve a semi-crystalline structure and a melting point in the range 60°Cto 170°C.

[020] The thermoplastic polymer or polymers may be selected from the list defined by copolymeric resins containing ethylene-vinyl acetate copolymers, ethylene-ethyl acrylate copolymers, ethylene-methyl acrylate copolymers, copolymers with alternating blocks of an amorphous butyl acrylate polymer between two crystalline polymethylmethacrylate polymers and copolyamides based on dimers obtained from a polycondensation reaction between a diacid and a diamine.

[021] The thermoplastic polymer or polymers may be an ethylene-vinyl acetate copolymer with a proportion of vinyl acetate in the range 18% to 40%, preferably equal to 28%.

[022] The ratio of the concentrations of the liquid amorphous thermoplastic resin to the polymers may be in the range l .5 to 2.

[023] The liquid amorphous thermoplastic resin may be selected from the list defined by rosin acid dérivatives esterified with methanol or with triethylene glycol, aromatic hydrocarbon resins with a molecular mass of less than 500 g/mole, hydroxylated polyester resins, polyisobutylenes and polyalkylmethacrylates.

[024] The thermoplastic dry films may also comprise one or more waxes selected from the list defined by paraffins, microcrystallme waxes, camauba waxes, polyethylene waxes, amide waxes and hydrogenated castor oils.

[025] The proportion by weight of waxes in the thermoplastic dry film may be in the range 3% to 20%.

[026] The dry thermoplastic films may also comprise particles of solid lubricants selected from the list defined by graphite, boron nitride, zinc oxide, molybdenum disulphide, graphite fluoride, tin sulphides, bismuth sulphides, thiosulfates, polytetrafluorethylene and polyamides.

[027] The proportion by weight of solid lubricant particles in the dry thermoplastic film may be in the range 2% to 20%.

[028] The dry thermoplastic films may also comprise a complex alkylarylsulphonîc acid sait neutralized with a calcium carbonate, the proportion by weight remaining below 40%.

[029] The dry thermoplastic films may also comprise a corrosion inhibitor, preferably calcium ion-exchanged silica, the proportion by weight of corrosion inhibitor being in the range 5% to 15% by weight.

[030] The dry thermoplastic films may also comprise a polydimethylsiloxane or perfluoropolyether oil, said oil having a kinematic viscosity in the range 100 to 1850 mm²/s at 20°C, the proportion by weight of said oil being in the range 2% to 10%.

[031] The first and second contact surfaces may already hâve been treated by means of a surface préparation step selected from the group constituted by sand blasting, conversion treatments and electrolytic déposition, before coating each surface with a dry thermoplastic film.

[032] Features and advantages of the invention will be described in more detail in the description which follows, made with reference to the accompanying drawîngs in which:

[033] Figure 1 is a diagrammatic view of a connection resulting from connecting two tubular components by makeup;

[034] Figure 2 is a diagrammatic view of a makeup curve for two threaded tubular components;

[035] Figures 3 to 7 represent test result curves;

[036] Figure 8 is a diagrammatic view of a test set-up;

[037] Figure 9 is a diagrammatic view of a connection configuration;

[038] Figure 10 is a diagrammatic view of a test set-up, [039] The invention is of application to threaded connections of the type shown in Figure 1, This type of connection comprises a first tubular component with an axis of révolution 10 provided with a male end portion 1 and a second tubular component with an axis of révolution 10 provided with a female end portion 2. The end portions 1 and 2 each hâve a terminal surface which is disposed perpendicular to their respective axis of révolution 10 and are respectively provided with a threaded zone 3 and 4 which cooperate mutually for mutual connection of the two components by makeup. The threaded zones 3 and 4 may be of the trapézoïdal, self-locking, or other thread type. Furthermore, metal/metal sealing surfaces 5, 6 intended to corne into sealed interfering contact against each other after connecting the two threaded components by makeup are provided respectively on the male 1 and female 2 end portions close to the threaded zones 3, 4. The male end portion 1 has a terminal surface 7 which can corne into abutment against a corresponding surface 8 provided on the female end portion 2 when the two components are made up one into the other. The connection also comprises two sealing surfaces 5 and 6 respectively disposed on the end portions 1 and 2 and intended to corne into sealed clamping contact when the connection is made up.

[040] Depending on the type of coupling or connection, the abutment between the terminal surface 7 and the corresponding surface 8 may also be replaced by self-locking interfering coopération of the threaded zones 3, 4 of the type described, for example, in US 4 822 081, US RE 30 467 or US RE 34467.

[041] Depending on the design or use requîrements, the end portions 1 and 2 of the tubular components may be partially or completely coated. As an example, the threaded zones 3 and 4 may be partially or wholly coated. This is also the case for the sealing surfaces 5 and 6 and for the abutment surfaces when they are provided at the end surface 7, and of the corresponding surface 8.

[042] We shall now discuss the genesis and details of the invention.

[043] The overall performance of a threaded tubular System consists of preventing adhesive wear by providing sufficient séparation of the surfaces in contact by means of sufficient lubricant and of guaranteeing the seal to gas of the connection in the abutment zone.

[044] Figure 2 shows a makeup curve for a connection, namely the increase in torque as a function of the number of tums and of the încreasing pressure in the contact zone. As can be seen, a makeup torque profile for “premium” connections can be broken down into four portions.

[045] At the start of makeup, the slope is small because the outer threads of the male threaded element (or “pin”) of a first component of a threaded tubular connection are not yet in radial interférence contact with the inner threads of a corresponding female threaded element (or “box”) of a second component of this same threaded tubular connection.

[046] Next, geometrical interférence of the threads of the male and female threaded éléments generates an încreasing radial interférence as makeup is continued (generating a small but încreasing makeup torque thereby).

[047] Next, the slope of the curve increases, which corresponds to the appearance of radial interférence between the sealing surfaces or even between the threads. This portion ends when the shouldering torque, ShT, is reached.

[048] The final portion ends when the abutment surfaces are in axial abutment and when the maximum admissible makeup torque, MTV, is reached.

[049] The maximum makeup torque MTV, which corresponds to the end of the final portion, is known as the plastification torque. Beyond this plastification torque, the male

makeup abutment (end portion of the male threaded element) and/or the female makeup abutment (zone located behind the annular abutment surface of the female threaded element) is/are assumed to hâve been subjected to plastic deformation, which might dégradé the performance of the sealing contact between the sealîng surfaces by plastification of the sealing surfaces as well.

[050] The différence between the values for the plastification torque MTV and the shouldering torque ShT is known as the torque on shoulder résistance. A threaded tubular connection is subjected to optimal tîghtenîng at the end of makeup, which guarantees optimal mechanical strength of the threaded connection, for example against tensile forces, but also against accidentai breakout in service, and also to optimal sealing performances.

[051] Good performance is characterized first of ail by a shouldering torque (ShT) which satisfies the following inequality:

(3) ShT < 0.56 MTV where MTV : maximum admissible torque.

The inequality (3) is related by the following inequalîties:

(1) ShT < 0.70 OT (2) OT < 0.80 MTV where OT: optimum torque.

This performance is also characterized by a large torque on shoulder résistance (AT) which generates sufficient energy at the unthreaded métal contact portion. Satisfying inequalîties (1) and (2) guarantees a great deal of flexibility in determining the optimum makeup torque as a function of the dimension and grade of connection. If at least one of the inequalîties is not satîsfîed, two major rîsks of weakening the performance of the connection arise:

• the risk of plastically deforming a portion of the abutment before having finished makeup in the case in which the torque on shoulder résistance is insufficient and the makeup torque is high;

• the risk of not shouldering at the unthreaded métal contact portion and of having incomplète makeup in the case in which the shouldering torque does not satisfy at least one of the équations (1) to (3).

[052] Currently, the greases used for connections, including heavy-metal free greases, satisiy this requirement and offer excellent performances irrespective of the dimensions and the grade of the connection. More precisely, oil-based greases, complex thickeners and lubricating or metallic solids combine two antagonîstic but complementary rheological properties: a flow behaviour with low friction in the hydrodynamic phase, and a “piezoviscous” behaviour in the lubrication phase under high pressure. The piezoviscosity corresponds to an increase in the vîscosity of the base oil under pressure. More particularly, this property is useful in lubricating mechanical Systems wherein the variation of the vîscosity of the oil dictâtes its proper operation. Devices for vaiying the speed, as is the case during makeup, require piezoviscous oils because of the difficulty of transmitting a torque between metallic parts which are not in contact and are subjected to high pressures.

[053] Other explanations hâve also been put forward, in particular in the case of API greases, indicating that metals such as lead and copper generate a high résistance to friction by crushing when the contact pressures increase.

[054] In the case of solid coatings, this antagonism may be overcome by adjusting the coefficient of friction by means of a plurality of solid coatings applied in different manners as a function of the makeup zone in order to carry out the various functions of lubrication, galling résistance and sealing, and primarily constituted by solid lubricants in a sacrificial hcat-curable binder. The solid lubricants also generate coefficients of friction in the range 0.02 to 0.12 depending on the chemical nature and the crystalline structure. The uncoated unthreaded métal contact portion thus just receives a surface préparation or a chemical conversion such as zinc phosphatation in order to artificially increase the value of the high pressure friction.

[055] Other successive approaches to solid thermoplastîc coatings hâve contributed to restoring low friction at high speeds and low contact pressures in the threading (150500 MPa), preserving a torque on shoulder résistance which is greater than or equal to the reference value for the API5A3 grease. To this end, a single coating is applied to

ίο either the threading or the sealing abutment and comprises a rheo-resistant material such as a “tackifying” solid resin with a softening point in the range 60°C to 200°C or a copolyamide resin in combination with a silicone or perfluorinated lubricating oil in a primarily viscoplastic matrix. During formation of a lubricating film, surface migration of lubricating oil compensâtes for the increase in the coefficient of friction resulting from résistance to movement under high pressure during makeup.

[056] However, investigation of a high torque on shoulder résistance is limited by mechanical éléments linked to free volume, to interférence between the two surfaces in contact, to machining tolérances, to the geometry of the connection and in particular to the thickness and to the surface of the area in contact in the unthreaded métal contact portion. The rheo-resistance approach by means of materials with a natural résistance to movement has în some cases provided evidence of limits in the capacity of the lubricating film to reagglomerate, namely to flow in the loading région and to maintain the third substance in the contact for as long a time as possible. One conséquence résides in the formation of extradâtes and flakes obtained from the highly elastic behaviour or even elastomeric behaviour of a lubricating film. The extradâtes and flakes are deleterious because they risk polluting the wells, in particular in the case of drilled wells operated in the North Sea and subject to the OSPAR convention (1998). The high résistance to movement of thermoplastic materials (polymers or resins) with a primarily amorphous structure is the resuit of a high elastic modulus under shear/compressive load and/or vitreous behaviour in the load/temperature domain associated with many secondary inter-molecular interactions (hydrophobie bonds, Van der Waals bonds, hydrogen bonds, polar bonds) which reinforce cohésion rather than adhesion to surfaces.

[057] It follows that in certain cases, the inequality (l) is not satisfied despite obtaining a large torque on shoulder résistance.

[058] In order to increase the capacity of the lubricating film to shear and flow in the température and load domain, it is possible to use crystalline waxes or crystalline metallic soaps with viscoplastic, ductile behaviour. However, there is a high risk of reducing the shear load, including under high pressures, and as a resuit of reducing the torque window which can be used to détermine the optimum makeup torque between high and low interférences of the connection.

[059] Thus, it is préférable to use a liquid amorphous thermoplastic resin which is sufficiently viscous to preserve the torque reserve by means of a supplémentai piezoviscous effect under high load and which is sufficiently adhesive and tacky to ensure re-agglomeration of débris from the lubricant film which is formed.

[060] In order to overcome the problems of solid thermoplastic coatings, the présent invention proposes forming a third substance which can correct the antagonism and is capable of both widening the makeup torque window and prolonging the Iife of the connection.

[061] The innovation consists of assocîatîng two solid thermoplastic coatings with synergistic performances at least one of which comprises a liquid amorphous thermoplastic resin with a dynamic viscosity in the range 2000 to 40000 mPa.s at 25°C. Figure 3 shows that if a product A applied to the male portion and to the female portion provides a low shouldering torque ShT and a low plastification torque MTV, and a product B applied to the male portion and to the female portion provides a high shouldering torque ShT and a high plastification torque MTV, then a connection coated with a product A on one side and B on the other can obtain a surprising resuit, namely a low shouldering torque ShT and a high plastification torque MTV.

[062] In order to prevent galling on each makeup and in order to guarantee a seal of the connection, a lubricating film must be maintained for as long as possible between the surfaces in contact. The lubricating film must also guarantee a comfortable reserve of torque in order to facilitate détermination of the optimum makeup torque irrespective of the grade of the connection (weight, diameter) and irrespective of the interférence type.

[063] The présent invention proposes applying to each of the zones of the connection which are to be brought into contact a coating with a matrix constituted by one more thermoplastic polymers which is solid and dry (i.e. not tacky to the touch), flexible, adhesive under load, rheo-resistant under high pressure and which demonstrates good lubricating properties.

[064] On just one of the two zones of the connection which are to be brought into contact, the solid thermoplastic coating also comprises a liquid amorphous thermoplastic resin with a dynamic viscosity in the range 2000 to 40000 mPa.s at 25°C. (i [065] The thermoplastic coating, supplemented with the liquid amorphous thermoplastic resin, may also comprise solid lubricants in order to improve the lubrication properties and waxes în order to adjust the shear loading and the thermomechanical properties.

[066] The thermoplastic polymer advantageously has a semi-crystalline structure and a melting point or softening point in the range 60°C to 170°C. If the melting point of the thermoplastic polymer is too high, it becomes difficult to apply the coating în its molten state, as is the case for coatings involving a process known as “hot melt”. If the melting point is too low, the solid lubricant film softens when it is exposed to high températures 10 such as in tropical régions or in summer in temperate régions, which may resuit in dégradation of performance.

[067] In particuiar, the thermoplastic polymers which may be used are copolymer resins contaîning polar groups such as ethylene-vinyl acetate copolymers, ethylene-ethyl acrylate copolymers, ethylene-methyl acrylate copolymers, and also copolymers with 15 altemating blocks of an amorphous butyl acrylate polymer between two crystalline polymethylmethacrylate polymers, and where the proportion of amorphous polymer is more than 70%.

[068] The semi-crystalline thermoplastic polymers may also be copolyamides based on dimers (hot melt polyamide) obtained from a polycondensation reaction between a 20 diacid (adipic acid, sebacic acid, dodecanoic acid, terephthalic acid) and a diamine (ethylenediamine, hexamethylenediamine, piperazine, polyoxyalkylenediamine, aromatic amines, dimerdiamine, branched dîamines). The copolyamides are selected for their capacity to adhéré by mechanical anchoring in the porous supports and principally by its amide functions onto polar supports. The dimer-based copolyamides are also 25 selected for their “rheo-resistance” property. The dimer-based copolyamides hâve a glass transition température in the range -55°C to 25°C, preferably less than -20°C, endowing them with a rubber-like behaviour in the load and température range which is représentative of makeup. The thermoplastic matrix may comprise just one or a mixture of dimer-based copolyamides in a concentration in the range 20% to 70% of the mass of the 30 lubricating film.

[069] In order to be supple and flexible, the thennoplastic copolymer will hâve a tensile strength of less than 10 MPa, an élongation at break in the range 10% to 1100%, preferably an élongation at break of less than 600%. The thennoplastic copolymer, preferably an ethylene-vinyl acetate copolymer, will hâve a proportion of vinyl acetate in the range 18% to 40%. A small proportion of vinyl acetate improves compatibility with the other constituents of the matrix, in particular the waxes. A high proportion of vinyl acetate increases solubility, improves flexibïlity and the strength of the film. An ethylene vinyl acetate copolymer with a proportion of vinyl acetate of 28% is preferred.

[070] So that the thennoplastic matrix can be adhesîve under load, the semicrystalline thennoplastic copolymer is generally compatibilized with a solid “tackifying” resin. The “tackifying” resin provides tack and vîscosîty above the softening température. The mixture will provide sufficient tack if the elastic modulus G’ is less than 10⁷ Pa in the loading and température région and too much if the modulus is less than 10⁶ Pa, as is the case with a pressure sensitive adhesîve (PSA), which would risk affecting the capacity of the film not to pîck up dust and pollutants. In other cases, it will be possible to select a thermoplastic polymer the adhesion mechanism of which is due to mechanical anchoring.

[071] The “tackifying” solid resin has a softening point in the range 60°C to 200°C, preferably higher than that of a thermoplastic polymer, in order to increase the elastic modulus, the viscosity or the rigidity of the mixture as a function of the température range, and as a conséquence the coefficient of friction. After having mixed the resin into the molten polymer, the resin becomes interposed, increases the mter-molecular interactions and disorganizes the crystalline structure of the polymer. The ratio between the polymer and the resin is preferably in the range 20/80 to 40/60 and the fraction of the amorphous structure in the thermoplastic matrix is more than 50% in order to adjust the “rheo-resistance” property. As the fraction of amorphous structure in a thermoplastic material or mixture is increased, “rheo-resistance”, measured with respect to the value for a reference API5A3 grease using a Bridgman test, increases near-asymptotically.

[072] In particular, the solid “tackifying” resins whîch may be used are resin acid or rosin acid dérivatives esterified with glycérine, pentaerythritol or polymerized rosin acid, or terpene, polyterpene or phenolic terpene resins, terpene styrene resins.

Incidentally, aliphatic and/or aromatic hydrocarbon resins may be used because their hîghly hydrophobie nature provides excellent moisture résistance and reduces the water vapour permeability.

[073] In order to adjust the rheological properties to the application, it is préférable to form a mixture of thermoplastic polymers, solid ‘hackifying” resin and waxes with different melting points or softening points in a wide range of températures. A wax does not only hâve an effect on preventing galling by reducing the shear load, and as a resuit the coefficient of friction, but it also contributes to increasing the fluidîty of the matrix in the molten state and of reducing the tack of the coating which is formed. The waxes may be of minerai (paraffin or micro-crystalline waxes), vegetable (camauba wax) or synthetic origin (polyethylene waxes, amide waxes or hydrogenated castor oil waxes). A mixture of a micro-crystalline wax with a high penetrability and a hydrogenated castor oil is préférable in order to increase the adhesion and ductility of the matrix. A proportion of waxes of more than 20% by weight in the coating could drastîcally reduce the “rheo-resistance”. A minimum of 3% by weight of wax is necessary in order to observe the effects described above.

[074] In order to increase the lubrication properties, the thermoplastic matrix may additionally contain different solid lubricating particles. The term “solid fabricant” as used here means a solid, stable substance which, on being înterposed between two frictional surfaces, can reduce the coefficient of friction and reduce wear and damage to the surfaces. These substances can be ciassified into different categories defined by their functional mechanism and their structure, namely:

• class 1 : solid substances owing their lubricating properties to their crystalline structure, for example graphite, boron nitride or zinc oxide;

• class 2: solid bodies owing their lubricating properties to their crystalline structure and also to a reactive chemical element in their composition, for example molybdenum disulphide MoS?., graphite fluoride, tin sulphides or bismuth sulphides;

• class 3: solid substances owing their lubricating properties to their chemical reactivity, for example certain chemical compounds of the thiosulphate type;

• class 4: solid substances owing their lubricating properties to a plastic or viscoplastic behaviour under frictional load, for example polytetrafluoroethylene (PTFE) or polyamides.

[075] Each of the classes of solid lubricants may be used; in particular, at least one lamellar film-effect lubricating solid from class 1 may be used, so that it does not interfère with the other properties. However, it is préférable to use a combination of several solid lubricants of a different class in order to increase the property as a function 10 of the nature of the surface. On a carbon steel coated with an electrolytic deposit of a CuSn-Zn alloy, it would be préférable to use a combination of a solid fabricant from class 2 with a sulphur chemical element for chemical absorption and a lubricating solid from class 4 in order to adjust the plastic behaviour under frictional load. The proportion of solid lubricated particles in the lubricating film is in the range 2% to 20% by weight.

[076] In order to improve the ductility, the anti-galling and protective effect against corrosion, it is possible to add a complex sait of an aromatic organic acid, preferably an alkylarylsulphonic acid neutralized with a calcium carbonate dispersed as colloïdal micro-particles in an oil. The alkali métal or alkaline-earth métal sait is in excess so that the alkalinity is in the range 250 to 450 mgKOH/g. At ambîent température, this substance generates a film which is both hydrophobie for a protective barrier effect against the corrosion mechanism, and lubricating on the one hand by physical absorption of the excess metallic sait and on the other hand by a chemical absorption of the organic acid function onto the métal surface. The concentration of complex aromatic organic acid sait does not exceed 40% by weight of the thermoplastic matrix. The lubricating film becomes semi-solid if the concentration is more than 40% by weight of the thermoplastic matrix.

[077] In order to reinforce the barrier effect and the anticorrosion property, the thermoplastic matrix may contaîn a corrosion inhibitor such as calcium ion-exchanged silica. The concentration of calcium-exchanged silica in the lubricating film is in the range

5% to 15% by weight, [078] In order in particular, to avoîd the phenomenon of “high shouldering”, it is préférable to sîgnificantly reduce the coefficient of friction for low fiictional loads (150 - 500 MPa) generated by the interférences of the threads and the surface at the moment of shouldering. In order to reduce the coefficient of friction, it is préférable to use a friction modifier which is not compatible with the other substances of the matrix in order to facilitate surface migration and not to affect the value of the “rheo-resistance”. The friction modifiera which may be used are oils with a low coefficient of friction (polydimethylsiloxane or perfluoropolyether) with a kinematic viscosity in the range 100 to 1850 mm²/s at 20°C. The proportion of polydimethylsiloxane oil is in the range 2% to

10% by weight in the coatîng.

[079] Finally, the solid thermoplastic coating may contain up to 2% by weight of other additives such as wetting agents, dispersing agents, dyes or, in particular, antioxidants in order to aid thermal stability of the polymera and thermoplastic resins in an oxidizing medium.

[080] The Applicant has demonstrated the performances of the association of two solid thermoplastic coatings at least one of which comprises a liquid amorphous thermoplastic resin, in accordance with the invention. To this end, the Applicant carried out comparative tests between conventional coatings and coatings in accordance with the invention, these tests being aimed on the one hand at evaluating the makeup torques 20 using a Bridgman test and on the other hand at evaluating the coefficients of friction by means of a Scratch test.

[081] The modified Bridgman tribometer can be used to evaluate the torque and the friction of surfaces in contact under high Hertz pressures. The Bridgman test device has in particular been described in the article by D Kuhlmann-Wilsdorf and al, “Plastic flow 25 between Bridgman anvils under high pressures”, J. Mater. Res., vol 6, no 12, Dec 1991.

A diagrammatic and functional example of a Bridgman machine is îllustrated in Figure 10. This machine comprises:

• a disk DQ which can be driven in rotation at selected speeds;

• a first anvil EC1, preferably conical in type, permanently attached to a first face of the disk DQ; pi • a second anvil EC2, preferably conical in type, permanently attached to a second face of the disk DQ, opposite its first face;

• first EPI and second EP2 pressure éléments, such as pistons, for example, which can exert the selected axial pressures P;

• a third anvil EC3, preferably cylindrical in type, which is permanently attached to one face of the first pressure element EPI ;

• a fourth anvil EC4, preferably cylindrical in type, which is permanently attached to one face of the second pressure element EP2.

[082] To test a lubricating composition, two pièces of a material identical to that constituting a threaded element are covered with said composition in order to form the first SI and second S2 specimens. Next, the first specimen SI is interposed between the free faces of the first EC1 and third EC3 anvils, and the second specimen S2 between the free faces of the second EC2 and fourth EC4 anvils. Next, the disk DQ is rotated at a selected speed while applying a selected axial pressure P (for example of the order of 1.5 GPa) with each of the first EPI and second EP2 pressure éléments, and the makeup torque to which each specimen SI, S2 is subjected is measured. The axial pressure, the rotatîonal speed and the angle of rotation are selected in the Bridgman test in order to sîmulate the Hertz pressure and the relative speed of the abutment surfaces at the end of makeup. Using such a machine, it is possible to fix several different pairings of parameters (makeup torque, rotation speed) in order to impose predetermined makeup torques on specimens SI and S2, and thus to check whether these specimens SI and S2 closely follow a given makeup torque profile, and in particular whether they can reach a number of completed turns before gallîng which is at least equal to a threshold value selected with respect to the selected makeup torques.

[083] In the présent case, the selected contact pressure was raîsed to 1 GPa and the rotatîonal speed was raised to 1 rpm. The test specimens were formed ffom carbon steel, machined then coated with different dry film formulations.

[084] The Scratch test device, shown diagrammatically in Figure 8, allows the adhesive force or adhesion of a film on a surface or surface préparation to be determined. This method, consisting of shearing and deforming a film with a spherical

bead subjected to an increasing load, also allows two tribological parameters which are important to the wear résistance to be determined, namely the coefficient of friction and the critical load corresponding to the appearance of a loss of film cohésion.

[085] The experimental conditions employ a spherical bead formed from tungsten carbide with a diameter of 5 mm and a métal specimen formed from XC or Z20C13 carbon steel with a roughness Ra of less than 1 micromètre, with optional surface préparation which may respectively be sand blasting, zinc or manganèse phosphatation, and a temary Cu-Sn-Zn electrolytîcal deposit. The parameters of the operating mode include a load increasing from 10 N to 310 N (with a load increase rate of 15 N/s), a rate of displacement of the bead of 2 mm/s, a duration of 20 s and a track length of 40 mm.

[086] Tests were carried out on a solid thermoplastic coating comprising a thermoplastic matrix constituted by an ethylene-vinyl acetate copolymer, a rosin acid esterified with glycérine with a softening point in the range 60°C to 200°C, waxes and a polydimethylsiloxane oil. This latter demonstrated a coefficient of friction of 0.07 to 0.08 under low pressure loads (approximately 200 MPa) and a “rheo-resistance” value in the range 90% to 100% of the value of the value of a API5A3 reference grease. In the case of makeup of a 7” 29# CS L80 VAM TOP HC connection where the solid thermoplastic coating is applied symmetrically to the male and female portion, the rheotribological properties of said coating mean that the makeup rules can be adhered to, namely a shouldering torque 70% below the optimum makeup torque defined for the connection and less than 56% of the maximum makeup torque but the absolute value of the maximum makeup torque, determined irrespective of machining interférences (LLPNBN or HH - PFBS) remain below the makeup torque of the “High Torque” VAM TOP reference connection for the same dimension (“liner max” makeup torque defined in the VAM Running Book), as can be seen in Figure 4. Figure 4 diagrammatically shows, as a histogram, values for the vertical overtorque makeup torque with a weight of 420 kg.

[087] Comparatively, a solid thermoplastic coating comprising a thermoplastic matrix primariiy constituted by copolyamides based on dimers, an amide wax and a polydimethylsiloxane oil had a coefficient of friction of 0.12 under the same conditions as before, and a “rheo-resistance” value of more than 105% of the value for a API5A3, reference grease. In the case of makeup of a 7” 23# CS L80 VAM21 connection where the solid thermoplastic coating is applied to the female portion and a protective epoxyacrylic resîn as described in document WO2010140703 is applied to the male portion, the good rheo-tribological properties of said coating could not satisiy the makeup raies wîth an optimum makeup torque of 17700 N.m. The lubricant film was particularly viscoelastic under frictional load, which affected the torque reserve, as is shown both by the increase in the shouldering torque and the réduction in the torque on shoulder résistance for increasîng machîning interférences. This high viscoelasticity does not allow the lubricating film to flow and adhéré in the load zone. The lubricating film is extraded from the contact, allowing unprotected métal to appear in a lîmiting lubrication phase. Galling rapidly occurs after 5 successive makeup/breakout operations.

[088] In order to evaluate the improvement in the overall performances of the coated connection, in one embodiment of the invention, a thermoplastic coating comprising a liquid amorphous thermoplastic resîn is applied to the other portion of the connection.

[089] In accordance with the invention, a liquid amorphous thermoplastic resin in a thermoplastic matrix provided with a property of “rheo-resistance” can be used to adapt the thermomechanical properties in order to increase the capacity of the lubricating film to shear and flow in the load/temperature zone.

[090] In the présent case, the thermomechanical properties were determined by compression/shear thermodynamic analysis (DMTA) using a “TTDMA T101423” apparatus supplied by Triton Technologie. The température was increased from -100°C to 100°C at 2°C/min; the strain frequency was 1 Hz and the deformation was imposed in the linear région.

[091] Figure 5 shows the change, in shear mode, of the elastic modulus (G’) and the viscous modulus (G”) of a lubricating film comprising a thermoplastic polymer of the copolyamide type based on dimers with and without liquid amorphous thermoplastic resin. The elastic modulus (or conservation modulus) is expressed in Pa and represents the real portion of the complex modulus M*. The viscous modulus (or loss modulus) represents the imaginary portion of the complex modulus M*.

[092] The variation in the elastic modulus G’ of a material comprising a liquid amorphous thermoplastic resin results in a shift in the softening point and the pour point

to lower températures. The increase in the viscous modulus G” results in a greater dissipation of energy in the form of heat during shear which is characteristic of an increase in its “rheo-resistance” by a softening effect.

[093] In addition, the “rheo-resistance” property is confirmed by a measurement 130% higher than the value of an API5A3 reference grease determined using the Bridgman test.

[094] At the same time, the variation in the coefficient of friction as a function of the încreasing load measured using the Scratch test in Figure 6 indicates that the value of the coefficient of friction generally increases with the load when the lubricating film is “rheo-resistant”. Conversely, a reference thermoplastic coating which is completely crystalline (described în patent W02009072486) is characterized by a stable or even decreasing coefficient of friction. Figure 6 represents the change in the coefficient of friction as a function of încreasing load.

[095] The liquid amorphous thermoplastic resins which may be used are dérivatives of rosin acid esterified with methanol or triethylene glycol, aromatic hydrocarbon resins with a molecular mass of less than 500 g/mole, hydroxylated polyester resins, polyisobutylenes or polyalkylmethacrylates. The liquid resîn must hâve a dynamic viscosity in the range 2000 to 40000 mPa.s at 25°C (measured with a Brookfield viscosimeter). A dynamic viscosity of more than 40000 mPa.s at 25°C exhibîts no împrovement in the thermomechanical properties. The liquid amorphous thermoplastic resîn must hâve a glass transition température of less than -10°C, preferably less than -20°C. The concentration of the liquid amorphous thermoplastic resîn in the thermoplastic matrix is in the range 40% to 60%. Preferably again, the concentration ratio of the liquid resîn to the polymer is in the range 1.5 to 2. A ratio of less than 1.5 reduces adhesion, while a ratio of more than 2 accentuâtes the capture of dust and pollutants (for example sand) by the film formed for a storage température of more than 50°C.

[096] In the case of makeup of a 7” 23# CS L80 VAM 21 connection in which the solid thermoplastic coating contains a liquid amorphous thermoplastic resin of the rosin acid type esterified with methanol is applied symmetrically to the male and female portion, the change in the thermomechanical behaviour of the lubricating film, namely a greater capacity for flow in the makeup load and température range, means that the formation of extradâtes and flakes can be considerably limited. At the same time, the^ supplemented “rheo-resistance” effect provided by the liquid amoiphous thermoplastic resin is manifested positively by an increase in the maximum makeup torque (MTV) and negatively by an increase in the shouldering torque. The value of the shouldering torque is slightly more than 70% of the value of the optimum makeup torque and increases with makeup/breakouts. Thus, coating the surfaces which are brought into contact in a symmetrical manner, i.e. ail with a solid thermoplastic coating which contains a liquid amoiphous thermoplastic resin, is not recommended.

[097] In accordance with the invention, a configuration in which the male and female surfaces which are brought into contact are coated with a solid thermoplastic coating one of which comprises a liquid amorphous thermoplastic resin shows a synergistic effect which is manifested by an improved thermomechanical behaviour and a broadening of the makeup torque window where the inequalities (l), (2) and (3) discussed above are satisfied.

[098] In order to illustrate the favourable thermomechanical behaviour of the third substance, a mixture of equal parts of two coatings with different compositions at least one of which contains a liquid amorphous thermoplastic resin was compared with a reference corresponding to a thermoplastic coating containing a solid “tackîfying” resin which was applied symmetrically to the two portions of the connection. Figure Ί shows that the elastic modulus G’ of the mixture (denoted Synergy in Figure 7) is lower than that of the reference (denoted Symmetrical in Figure 7). This is the same for the viscous modulus G”. The third substance obtained was of a nature to reconcile the thermomechanical properties of each of the coatings with the aim of increasing the overall performance. Smaller moduli and maïntaining the ratio between the moduli G2 and G’ resuit in a lower résistance to shear and conservation of the rheo-resistance property.

[099] The Applicant has also carried out a certain number of tests in order to quantify the performances of the association of two solid thermoplastic coatings at least one of which comprises a liquid amorphous thermoplastic resin in accordance with the invention.

[0100] In terms of experimental conditions, the thermoplastic coating is formed using a “hot melt” method on the part to be coated, namely the threading zone, the unthreaded métal contact portion and/or the abutment surfaces.

[0101] According to the “hot melt” method, the composition comprising a thermoplastic matrix, additives and powders is melted to provide a sufficiently low viscosity for the coating to be capable of being applied by pneumatic spraying using a gun with the capacity to maintain a fixed température close to the température at which the composition is in the molten state. The température to which the composition is heated is preferably in the range 10°C to 50°C above the melting point of the thermoplastic matrix. Advantageously, the température will be in the range 130°C to 160°C such that the complex viscosity under shear (measured using a plane/plane rheometer) is less than 20 Pa.s. The substrate to be coated is preferably pre-heated to a température greater than or equal to the température of the molten composition in order to facilitate wetting and spreadîng.

[0102] The composition, heated and melted in a réservoir equipped with mechanical agitation means, is sent to a gun by means of a pump and sprayed onto the substrate.

[0103] The substrate is then cooled with air or CO2 în order to solidify the thermoplastic matrix and form the solid thermoplastic lubricating film.

[0104] The thickness ofthe lubricating film formed is preferably în the range 25 to 100 pm. If it were thinner, it would not be thîck enough to provide the antî-galling property as well as the corrosion résistance. A thickness above thîs range generates naturel extrusion of the excess and a supplémentai risk of environmental pollution.

[0105] Alternatively, the composition may be dissolved in an organic solvent with a boiling point of more than 150°C for direct application to a cold substrate without passing through a step for melting the thermoplastic matrix. The solid thermoplastic lubricating film is then preferably applied to a rough surface. Figure 9 diagrammatically shows a configuration of the connection comprising a substrate 100 or 200, a surface préparation 101, 201, 203 and the solid thermoplastic lubricating film 102 or 202. A rough surface increases the contact surface area and as a resuit increases the adhesion and the lubricant rétention capacity in particular in the limiting lubricatîon phase. The roughness of the surface may be obtained by mechanical sand blasting of the steel or by means of a surface préparation using chemical conversion, such as zinc or manganèse phosphatation.

[0106] Preferably, the mean roughness, Ra, is in the range I to 3.5 μιη. and the maximum peak height or Rmax is in the range 5 to 25 μιη.

[0107] The thickness of the film formed must be at least greater than the maximum peak height or Rmax.

[0108] The substrate may be formed from carbon steel or a stainless steel with at least 13% Cr. In order to increase the galling résistance of the steel and especially of stainless steel with at least 13% Cr, an electrolytic deposit of copper or, preferably, a Cu-Sn-Zn temary alloy may be deposited on a layer of Ni at the surface of the substrate. An electrolytic Cu-Sn-Zn deposit increases the hardness and ensures supplémentai séparation of the male and female surfaces in the contact zone in order to prevent galling.

[0109] Advantageously, at least one of the two surfaces in contact undergoes mechanical sand blasting (203) with a maximum depth in the range 10 to 25 μιπ.

[0110] Firstly, the Applicant demonstrated the effects of the présent invention by employing it with various types of connections (denoted Example 1 to Example 2) and by comparing these variations with connections coated with conventional films (denoted comparative examples 1 to 6).

[0111] The grade and the dimensions of the carbon steel connection and the detail of the male and female surface préparations are shown in Table 1.

Examples	Connection	Surface préparation
Male portion	Female portion
Example n°l	7” 29# L80 VAM TOP	Zinc phosphatation (Rmax = 5pm)	Manganèse phosphatation (Rmax = 11 pm)
Example n°2	9”5/8 47# L80 VAM TOP	Zinc phosphatation (Rmax = 5pm)	Cu-Sn-Zn electrolytic deposit + Ni layer (Th = 12pm)
Comparative example No.l	7” 23# L80 VAM 21	Zinc phosphatation (Rmax = 5pm)	Manganèse phosphatation (Rmax = 11 pm)
Comparative example No.2	7” 29# L80 VAM TOP	Zinc phosphatation (Rmax = 5pm)	Manganèse phosphatation (Rmax = 11 pm)
Comparative example No.3	9”5/8 47# L80 VAM TOP	Zinc phosphatation (Rmax = 5pm)	Cu-Sn-Zn electrolytic deposit + Ni layer (Th = 12pm)
Comparative example No.4	7” 23# L80 VAM 21	Zinc phosphatation (Rmax = 5pm)	Manganèse phosphatation (Rmax = llpm)
Comparative example No.5	7” 23# L80 VAM 21	Zinc phosphatation (Rmax = 5pm)	Manganèse phosphatation (Rmax = 11 pm)
Comparative example No.6	7” 23# L80 VAM 21	Zinc phosphatation (Rmax = 5pm)	Cu-Sn-Zn electrolytic deposit + Ni layer (Th=12pm)

Table 1 where: Rmax : maximum peak height, and Th: thîckness of layer [0112] The composition of the lubricating films is shown in Table 2 for each example and each comparative example. The percentages are with respect to the total composition weight.

[0113] tn order to illustrate the effects of the présent invention, in particular broadening of the torque window, the Applicant determined the maximum torque on shoulder résistance prior to plastification (or overtorque). In order to illustrate the effects of the présent invention on the galling résistance, the Applicant determined the number

of makeup/breakout operations carried out at the makeup torque of the connection and the mean shouldering torque value. The results are shown in Table 3.

[0114] In each test, makeup was carried oui with longs in the vertical position with a weight of 420 kg. The makeups were carried out 10 times and a makeup was carried out at a speed of 10 and 15 turns per minute at the start of makeup and at a speed of 1 and 2 turns per minute at the end of makeup in the abutment zone. After breakout, the state of galling of the male and female portions was inspected visually. The presence of flakes or extrusion, corresponding to a weak capacity of the third substance to re-agglomerate in the contact, was synonymous with inappropriate thermomechanical behavîour.

[0115] Example No. 1 : A solid thermoplastic coating with a thermoplastic matrix which did not contain a liquid amorphous thermoplastic resin, but rather a solid “tackifying” resin with a softening point in the range 60°C to 200°C was applied to the female portion and a solid thermoplastic coating the matrix of which comprised a liquid amorphous thermoplastic resin was applied to the male portion of a 7” 29# L80 VAM TOP connection. The optimum makeup torque was 17750 N.m. An increase of 80% in the torque window was measured, with no effects on the shouldering torque compared with comparative example No. 2. No extrusion or formation of flakes indicated that there was a synergistic effect in the re-agglomerating thermomechanical behavîour of the third substance. No severe galling was observed after 10 makeup/breakout operations.

[0116] Example No. 2: A solid thermoplastic coating with a thermoplastic matrix which did not contain a liquid amorphous thermoplastic resin, but rather a solid “tackifying” resin with a softening point in the range 60°C to 200°C was applied to the female portion and a solid thermoplastic coating the matrix of which comprised a liquid amorphous thermoplastic resin was applied to the male portion of a 9 5/8” 47# L80 VAM TOP connection. The optimum makeup torque was 19200 N.m. An increase of 13% in the torque window and a significant increase in the torque on shoulder résistance of 60% confirmed the synergistic effect. An overall increase in protection against galling was also visible. No galling was observed after 10 makeup/breakout operations.

[0117] Comparative example No. 1: A Bestolife 4010NM viscous grease containing no heavy metals which are dangerous to the environment, such as lead, was applied to the male portion and the female portion of a 7” 23# L80 VAM 21 connection in order to

form a lubricating film. The quantity of grease applied to the surfaces in contact was 50g. The maximum torque on shoulder résistance before plastification determined by the overtorquing test for high machining interférences (HH - PFBS) was 13950 N.m. The torque on shoulder résistance for each example was compared with this reference value of 100. The makeup/breakouts were concatenated, renewing the grease between each makeup and were carried out to the optimum makeup torque, namely 16400 N.m. No galling was observed after 10 makeup/breakout operations on the connection.

[0118] Comparative example No. 2: A solid thermoplastic coating with a thermoplastic matrix which did not contain a liquid amorphous thermoplastic resin, but rather a solid “tackifying” resin with a softening point in the range 60°C to 200°C was applied to the male and female portions of a 7” 29# L80 VAM TOP connection. The optimum makeup torque was 16000 N.m. In order to evaluate the capacity of the lubricating film to protect the substrate or the surface préparation against corrosion, the thermoplastic coating was applied to specimens (100 mm x 150 mm x 0.8 mm) formed from carbon steel with the same surface préparation. The specimens underwent a saline mist test (in accordance with ISO standard 9227, température 35°C for 500 hours), a condensationwater atmosphère test (in accordance with ISO standard 6270, température 40°C, relative humidity 95% for 1000 hours) and an accelerated climate or cyclic corrosion test représentative of extreme storage conditions (in accordance with VDA standard 621415, for 3 cycles). No rust was observed at the end of the three tests.

[0119] Comparative example No. 3: A solid thermoplastic coating with a thermoplastic matrix which did not contain a liquid amorphous thermoplastic resin, but rather a solid “tackifying” resin with a softening point in the range 60°C to 200°C was applied to the female portion and an epoxy-acrylic resin cured with ultraviolet light comprising a polyethylene wax and a corrosion inhibitor of the aluminium polyphosphate type was applied to the male portion of a 9 5/8” 47# L80 VAM TOP connection. The optimum makeup torque was 18900 N.m. No rust was observed at the end of the three tests, namely saline mist, condensation-water atmosphère and cyclic corrosion.

[0120] Comparative example No. 4: A solid thermoplastic coating with a thermoplastic matrix which did not contain a liquid amorphous thermoplastic resin, but rather a solid “tackifying” resin with a softening point in the range 60°C to 200°C was applied to the male and female portions of a 7” 23# L80 VAM 21 connection. The optimum makeup torque was 17500 N.m. Severe galling in the threading was recorded at the 10^th makeup/breakout operation. The abutment surfaces were intact. In order to détermine the seal of the unthreaded métal contact portion of a connection under well conditions, a high température (180°C) sealing test under extemal pressure was carried out in accordance with the procedure in ISO standard 13679: 2011, No leakage was observed at the end of the test for comparative example No. 2.

[0121] Comparative example No. 5: A solid thermoplastic coating with a thermoplastic matrix which contained a liquid amorphous thennoplastic resin was applied to the male and female portions of a 7” 23# L80 VAM 21 connection. The optimum makeup torque was 17500 N.m. The value for the shouldering torque was 70% higher than the value for the optimum torque from the 6^ÜI makeup/breakout operation. Severe galling in the threading was detected at the 9'^h makeup/breakout operation, but the abutment surfaces were intact. However, makeup was stopped because the mechanical properties of the connection were no longer guaranteed. The lubricating film completely protected the surface préparation because no rust had appeared at the end of the three tests, the saline mist, condensatîon-water atmosphère and cyclic corrosion tests.

[0122] Comparative example No. 6: A solid thermoplastic coating the matrix of which was completely crystalline was applied to the female portion and an epoxy-acrylic resin cured by ultraviolet light comprising a polyethylene wax and an aluminium polyphosphate type corrosion inhibitor was applied to the male portion of a 7” 23# L80 VAM 21 connection. The optimum makeup torque was 10800 N.m. No galling was observed after 10 makeup/breakout operations of the connection. In contrast, the maximum makeup torque was much lower than the optimum makeup torque with API5A3 reference grease for a “High Torque” connection with the same dimensions. The unthreaded métal contact portion was at risk of being plasticized before reaching the optimum makeup torque. In this case, such a lubricating solution could not be extended to ail grades of the connections.

Claims (10)

1. An assembly for the production of a threaded connection, comprising a first and a second tubular component each with an axis of révolution (10) and each provided at one of their ends (1,2) with a threaded zone (3; 4) produced on the outer or inner peripheral surface of the component depending on whether the threaded end is male or female in type, said ends (1,2) being capable of cooperating by makeup and ending in a terminal surface (7, 8), at least one first contact surface being provided on one of the ends (1,2) and at least one second contact surface being provided on the corresponding end (1, 2), such that the first and second contact surfaces come into contact during makeup ofthe ends (1,2), characterized in that the first and second contact surfaces are respectively each coated with a first and a second dry thermoplastic film the matrices of which are constituted by one or more thermoplastic polymers, only one of the first and second dry thermoplastic films further comprising a liquid amorphous thermoplastic resin with a dynamic viscosity in the range 2000 to 40000 mPa.s at 25°C.

2. An assembly for the production of a threaded connection according to claim 1, characterized in that the first and second contact surfaces comprise a portion of the threaded zones (3; 4).

3. An assembly for the production of a threaded connection according to any one of the preceding claims, characterized in that the first and second contact surfaces comprise sealing surfaces provided on the circumferential surface of the ends (1,2) of the first and a second tubular components.

4. An assembly for the production of a threaded connection according to any one of the preceding claims, characterized in that the first and second contact surfaces comprise abutment surfaces provided on the terminal surfaces (7,8) of said ends (1,2).

5 17. An assembly for the production of a threaded connection according to any one of the preceding claims, characterized in that the dry thennoplastic films also comprises a polydimethylsiloxane or perfluoropolyether oil, said oil having a kinematic viscosîty in the range 100 to 1850 mm²/s at 20°C, the proportion by weight of said oil being in the range 2% to 10%.

5. An assembly for the production of a threaded connection according to any one of the preceding claims, characterized in that the thermoplastic polymer or polymers constituting the matrix of the first and second dry films hâve a semi-crystalline structure and a melting point in the range 60°C to 170°C.

6. An assembly for the production of a threaded connection according to any one of the preceding claims, characterized in that the thermoplastic polymer or polymers is or are selected from the list defined by copolymeric resins contaîning ethylene-vinyl acetate copolymers, ethylene-ethyl acrylate copolymers, ethylene-methyl acrylate copolymers, copolymers with altemating blocks of an amorphous butyl acrylate polymer between two crystalline polymethylmethacrylate polymers and copolyamides based on dimers obtained from a polycondensation reaction between a diacid and a diamine.

3l

7. An assembly for the production of a threaded connection according to the preceding claim, characterized in that the thermoplastic polymer is an ethylene-vinyl acetate copolymer with a proportion of vinyl acetate in the range 18% to 40%, preferably equal to 28%.

5

8. An assembly for the production of a threaded connection according to any one of the preceding claims, characterized in that the liquid amorphous thermoplastic resin included in only one of the first and second dry thermoplastic films has a glass transition température of less than -10°C, preferably less than -20°C.

9. An assembly for the production of a threaded connection according to any one of the

10 preceding claims, characterized in that the ratio of the concentrations of the liquid amorphous thermoplastic resin to the polymers is in the range 1.5 to 2.

10. An assembly for the production of a threaded connection according to any one of the preceding claims, characterized in that the liquid amorphous thermoplastic resin is selected from the list defined by rosin acid dérivatives esterified with methanol or with

15 triethylene glycol, aromatic hydrocarbon resins with a molecular mass of less than 500 g/mole, hydroxylated polyester resins, polyisobutylenes and polyalkylmethacrylates.

11. An assembly for the production of a threaded connection according to any one of the preceding claims, characterized in that the thermoplastic dry films also comprise one or more waxes selected from the list defined by paraffins, microcrystalline waxes, camauba

20 waxes, polyethylene waxes, amide waxes and hydrogenated castor oils.

12. An assembly for the production of a threaded connection according to the preceding claim, characterized in that the proportion by weight of waxes in the thermoplastic dry film is in the range 3% to 20%.

13. An assembly for the production of a threaded connection according to any one of the

25 preceding claims, characterized in that the dry thermoplastic films also comprise particles of solid lubricants selected from the list defined by graphite, boron nitride, zinc oxide, molybdenum disulphide, graphite fluoride, tin sulphides, bismuth sulphîdes, thiosulfates, polytetrafluorethylene and polyamides.

14. An assembly for the production of a threaded connection according to the preceding

30 claim, characterized in that the proportion by weight of solid fabricant particles in the dry thermoplastic film is in the range 2% to 20%.

15. An assembly for the production of a threaded connection according to any one of the preceding claims, characterized in that the dry thermoplastic films also comprise a complex alkylarylsulphonic acid sait neutralized with a calcium carbonate, the proportion by weight remaining below 40%

16. An assembly for the production of a threaded connection according to any one of the preceding claims, characterized in that the dry thermoplastic films also comprises a corrosion inhibitor, preferably calcium ion-exchanged silica, the proportion by weight of corrosion inhibitor being ΐη the range 5% to 15% by weight.

10 18. An assembly for the production of a threaded connection according to any one of the preceding claims, characterized in that the first and second contact surfaces hâve already been treated by means of a surface préparation step selected from the group constituted by sand blasting, conversion treatments and electrolytic déposition, before coating each surface with the dry thermoplastic filmai