OA18450A - Threaded tubular element provided with a metallic anti-corrosion and anti- galling coating - Google Patents

Abstract

The invention concerns a threaded portion of a tubular element for a threaded tubular connection hiving an axis of revolution, the portion comprising a threading extending over its outer or inner peripheral surface, and a first sealing surface on the peripheral surface, the first sealing surface being capable of producing metal-metal interference with a corresponding second sealing surface belonging to a complementary threaded portion of a tube. The threading and the first sealing surface are coated with a metallic anticorrosion and anti-galling layer wherein zinc (Zn) is tie major element by weight.

Description

[001] The présent invention relates to a tubular element for drilling and/or operating a hydrocarbon well, and more precisely to the threaded end of an element of this type. This end may be male or female in type, and is capable of being connected to a corresponding end of an analogous element in order to form a joint or connection.

[002] The invention also relates to a threaded connection resulting from connecting two tubular éléments by makeup, one of which may be a coupling with two female ends.

[003] The term “tubular element for drilling and operating a hydrocarbon well” means any element with a substantially tubular shape which can be connected to another element which may or may not be of the same type, with a particular view of constituting either a hydrocarbon well drill string or a work-over riser or operating this kind of string such as a riser, or a casing or tubing string used in operating a well. The invention is also applicable to the éléments used in a drill string such as, fer example, drill pipes, heavy weight drill pipes, drill collars and tool joints.

[004] Each tubular element comprises an end portion with a male threaded zone or a female threaded zone which îs intended to be made up with a corresponding end portion of an analogous element. When connected, the éléments compose what is known as a joint or connection.

[005] These threaded tubular components of a connection are connected under predefined loads in order to respond to the clamping and seal demands imposed by the conditions ofuse; more precisely, a pre-defined torque is aimed for. Further, it should be known that the threaded tubular components may hâve to undergo several cycles of makeup and breakout, in particular in service.

[006] The conditions for use of these threaded tubular components give rise to different types of loads. They hâve been reduced, inter alia, by using films or greases on the sensitive parts of these components such as the threaded zones, the abutment zones or indecd the metal/metal sealing surfaces.

[007] Induced constraints in particular include constraints due to being kept in storage, neccssitating the application of storage greases (different from makeup greases applied before being put into service). However, other solutions exist, consisting of using organic coatings.

[008] Thus, makeup operations are usually carried out under a high axial load, for example because of the weight of a tube several mètres long to be connected via the threaded connection, possibly aggravated by a slight misaltgnment of the axis of the threaded éléments to be connected. Thîs induces rîsks of galling in the threaded zones and/or in the metal/metal sealing surfaces. Thus, the threaded zones as well as the 10 metal/metal sealing surfaces are routinely coated with fabricants.

[009] Furthermore, the threaded tubular components are often stored then made up in an aggressive environment. This is the case, for example, in an “offshore situation in the presence of a saline mist, or in an “onshore” situation in the presence of sand, dust and/or other pollutants. Thus, it is necessary to employ different types of coating against 15 corrosion on the surfaces which are loaded during makeup, which is the case with the threaded zones or indeed in zones in clamping contact, which is the case with the metal/metal sealing surfaces and the abutments.

[010] However, having regard to envîronmentai standards, it appears that using greases complying with the standard API RP 5A3 (American Petroleum Jnstitute) does 20 not constitute a long-term solution, since such greases are caused to be extruded from the tubular components and released into the environment or into the well, causing blockages which necessitate spécial cleaning operations [011] In order to respond to the problems of a long-lasting résistance to corrosion, galling and to prérogatives associated with environmcntal considérations, an alternative 25 to greases has been developed. They not only provide a response to corrosion résistance performance and galling performance, but also to the industrial constraints involved in fabricating threaded ends.

[012] Since 1969, WHITFORD (registered trade mark) has proposed high performance coatings produced from a mixture of polyamide-imide resin and 30 fluoropolymers for threaded fasteners, which necessitate adapting the friction in rapid makeup/breakout operations.

[013] Furthermore, since 2002, in the context of threaded connections, coatings based on polyamide-imide resin hâve been proposed to lubricate and guarantec the résistance to galling during makeup, as described in documents EP 1 378 698 and EP 1 959 179.

[014] That prior art principally proposes obtaining dry films from a polyamide-amie acid precursor dissolved in a polar solvent or in an ethanoVtofaene mixture. The dry film ts generally applied in order to ensure fabrication as a fonction ofthe contact pressures in the threading. The proportion of fillcrs is relatively high, with a pigment/binder weight ratio in the range 025 to 4, preferably more than 3. The dry film is thus advantageously sacrificial and sufficientiy résistant to wear during fonctioning of the solid fabricant [015] Application WO 2004/033951 concems a threaded metallic tube for the oil extraction industry with a threaded end portion the surface of which is treated and in which the metallic surface has a surface roughness (Ra) in the range 2.0 gm to 6 gm, this surface being covered with a uni form layer of a dry anti-corrosion coating and with a second, uniform layer of a dry fabricant coating. Altematively, the two layers may be combined into a single layer of a dry anti-corrosion coating comprising a dispersion of particles of dry fabricant Nevertheless, the dispersion of particles over lhe anti-corrosive layer deposited on the substrate introduces a certain amount of hcterogencity.

[016] In addition, the application EP 2 128 506 concems a threaded connection of the male/femalc type for steel tubes having a contact surface comprising a threaded portion and a non-threaded metal-on-metal contact portion. The surface of at least one ofthe male or female éléments is coated with a first laminating layer produced from a Cu-Zn alloy or a Cu-Zn-MI alloy (where Ml is at least one element selected from Sn, Bi and In). In spite of the interesting results with these layers containing copper, the anti-corrosive properties associated with them hâve been shown to hâve limita which it would be désirable to overcome.

[017] Thus, the corrosion and galling behaviour of those disclosures could be improved by proposing, în addition to the functional properties of corrosion performance and good galling résistance, and a seal to gas and to liquid for the connections of the invention disclosed below. Based on this concept, the présent invention proposes coating a threaded element or a connection formed by connecting threaded éléments intended for drilling and/or operating hydrocarbon wells.

DISCLOSURE OF THE INVENTION [018] In a first aspect, the invention pertains to a threaded portion of a tubular element for a threaded tubular connection for drilling or operating hydrocarbon wclls, having an axis of révolution, said portion comprising a threading extending over its outer or inner peripheral surface, and a first sealing surface on said peripheral surface, said first sealing surface being capable of producing metal-metal interférence with a corresponding second sealing surface belongîng to a complementary threaded portion of a tube, characterized in that said threading and said first sealing surface are coated with a metallic anti-corrosion and anti-galling layer wherein zine (Zn) is the major element by weight [019] Preferably, the metallic anti-corrosîon and anti-galling layer is deposîted electrolytically.

[020] Preferably, the metallic anti-corrosion and anti-galling layer contains at least 50% by weight of zinc (Zn).

[021] Preferably, the metallic anti-corrosion and anti-galling layer has a thickness in the range 4 pm to 20 pm.

[022] Preferably, the metallic anti-corrosion and anti-galling layer comprises a substance selected from the group constituted by pure zinc (Zn) and a binary alloy of zinc (Zn) of the type Zn-X, in which X is selected from nickel (Ni), Iron (Fe), magnésium (Mg) and manganèse (Mn). Preferably, the metallic anti-corrosion and antigalling layer is a zinc-nickel (Zn-Ni) alloy wherein the nickel (Ni) content îs in the range 12-15% by weight and wherein the microstructure is monophase and in the gamma (γ) phase.

[023] Preferably, the metallic anti-corrosîon and anti-galling layer is coated with a fabricant layer comprising a resin and a dry solid fabricant powder dispersed in said resin.

[024] Preferably, the metallic anti-corrosion and anti-galling layer is coated with a passivation layer comprising trivalcnt chromium (CrflII)), said passivation layer being formed between the metallic layer and the fabricant layer.

[025] Preferably, the metallic anti-corrosion and anti-galling layer is coated with a passivation layer comprising trivalent chromîum (Cr(III)).

[026] Preferably, the passivation layer is coated with a barrier layer constituted by a minerai matrix hyer comprising particles of silicon dioxide (SiCh).

[027] Preferably, the passivation layer is coated with a barrier hyer constituted by an organo-mineral matrix layer comprising particles of silicon dioxide (SÎOi).

[028] Preferably, the portion further comprises a first abutment which is capable of comtng înto contact, at the end of makeup, with a corresponding second abutment and belonging to a complementary threaded tube portion.

[029] Preferably, the threaded portion is produced from steel.

[030] In an alternative, the threaded portion is male in type, with a threading extending over its outer peripheral surface as well as a first sealing surface on said outer peripheral surface.

[031] In another alternative, the threaded portion is female in type, with a threading 15 extending over its inner peripheral surface as well as a first sealing surface on said inner peripheral surface. ' [032] In a second aspect, the invention pertains to a threaded portion of a tubular élément for a threaded tubular connection for drilling or operating hydrocarbon wells, having an axis of révolution, saîd portion comprising a threading extending over its outer 20 or inner peripheral surface, and a first sealing surface on said peripheral surface, saîd first sealing surface being capable of producing mctal-metal interférence with a corresponding second sealing surface belonging to a complementary threaded portion, characterized in that said threading and said first sealing surface are coated with a metallic anti-galling layer wherein zinc (Zn) is the major element by weight, said metallic anti25 galling layer being at least partially coated with a lubricant hyer comprising a resta and a dry solid lubricant powder dïspersed in said resta.

[033] In a preferred manner, the metallic anti-galling layer in this threaded portion is deposited electrolytically.

[034] In a preferred manner, the metallic anti-galling hyer contains at least 50% by 30 weight ofzinc (Zn).

[035] In a preferred manner, the métal lie anti-galling layer has a thickness in the range 4 pm to 20 pm.

[036] In a preferred manner, the fabricant layer has a thickness în the range 5 pm to 50 pm.

[037] In a preferred manner, the metallîc anti-galling layer comprises a substance selected from the group constituted by pure zinc (Zn) and a binary alloy of zinc (Zn) of the type Zn-X, in which X is selected from nickel (Ni), iron (Fe), magnésium (Mg) and manganèse (Mn). In a preferred manner, the metallic anti-galling layer is a binary zincnickel (Zn-Ni) alloy wherein the nickel (Ni) content îs in the range 12-15% by weight and wherein the microstructure is monophase and in the gamma (γ) phase.

[038] In a preferred manner, the threaded portion of the invention comprises a passivation layer comprising trivalent chromîum (Cr(lII)), said passivation layer being formed between the metallic anti-galling layer and the fabricant layer.

[039] In a preferred manner, the dry solid fabricant powder is selected from the group constitutcd by polytetrafluoroethylenes (PTFE), molybdenum dithiocarbamatcs (MoDTC), molybdenum disulphidcs (MoSj), carbon blacks (C), graphite fluorides (CF,) or a mixture thereof.

[040] In a preferred manner, the resin is selected from the group constitutcd by polyvinyl resins, epoxy resins, acrylic resins, polyuréthane resins and polyamide-îmide resins.

[041] In a preferred manner, the resin is ofthe acrylic type and the dry solid fabricant powder contains 3% to 15% of carbon blacks, MoSj or molybdenum dithiocarbamatcs (MoDTC), alone or în combination.

[042] In a preferred manner, the threaded portion ofthe invention further comprises a first abutment which is capable of coming into contact, at the end of makeup, with a corresponding second abutment belongtng to a complementary threaded portion.

[043] In a preferred manner, the threaded portion is produced from steel.

[044] In one case, the threaded portion is male in type, with a threading extending over its outer peripheral surface, as well as a first sealing surface on said outer peripheral surface.

[045] In another case, the threaded portion of the invention is female in type, with a * threading extending over its tnner pcriphcral surface as well as a first sealing surface on said inner peripheral surface.

[046] In a third aspect, the Invention pertains to a threaded tubular connection for drilling or operating hydrocarbon wclls, comprising a portion of a tubular element with a male end having an axis of révolution and provided with a first threading extending about the axis of révolution, said male end portion being complementaiy with a portion of a tubular element with a female end having an axis of révolution and provided with a second threading extending about the axis of révolution, said male and female end portions being capable of being connected by makeup, each of the male and female end portions further comprising a sealing surface with a metal-metal interférence, characterized in that the threading and the sealing surface of one of the two, male or female, end portions are coated with a first métal lie anti-corrosion and anti-galling layer wherein zinc (Zn) is the major element by weighL said first metallic anti-corrosion and anti-galling layer being coated with a first passivation layer, the threading and sealing surface of the male or female complementary portion being coated with a second metallic anti-galling layer wherein zinc (Zn) is the major element by weighL said second metallic anti-galling layer being at least partially coated with a lubricant layer comprising a resta and a dry solid fabricant powder dispersed in said resta.

[047] Preferably, the threaded tubular connection ofthe invention is such that at least one ofthe first and second metallic layers is deposited electrolytically.

[048] Preferably, the threaded tubular connection of the invention is such that at least one of the first and second metallic layers contains at least 50% by weight of zinc (Zn).

[049] Preferably, the threaded tubular connection ofthe invention is such that at least one of the first and second metallic layers has a thickness in the range 4 pm to 20 pm.

[050] Preferably, the lubricant layer has a thickness in the range 5 pm to 50 pm.

[051] Preferably, the threaded tubular connection ofthe invention is such that at least one of the first and second metallic layers comprises a substance selected from the group constituted by pure zinc (Zn) and a binary alloy ofzinc (Zn) ofthe type Zn-X, in which X is selected from nickel (Ni), iron (Fe), magnésium (Mg) and manganèse (Mn). Preferably, the threaded tubular connection of the invention Is such that at least one of the first and second metallic layers is a binary zinc-nickel (Zn-Ni) alfoy wherein the nickel (Ni) content is in the range 12-15% by weight and wherein the mie restructure is monophase and in the gamma (y) phase.

[052] Preferably, the first passivation layer comprises trivalent chromium (Cr(III)).

[053] Preferably, the threaded tubular connection of the invention is such that a second passivation layer comprising trivalent chromium (Cr(III)) is formed between the second metallic anti-galling layer and the lubricant layer.

[054] Preferably, the dry solid lubricant powder is selected from the group constituted by polytetrafluoroethylenes (FTFE), molybdenum disulphides (MoSi), molybdenum dithiocarbamates (MoDTC), carbon blacks (C), graphite fluorides (CF_X) or a mixture thereof.

[055] Preferably, the threaded tubular connection in accordance with the invention is such that the resin is selected from the group constituted by polyvinyl res ins, epoxy resins, acrylic resins, polyuréthane restas and polyamide-imide restas.

[056] Preferably, the resin is ofthe acrylic type and the dry solid lubricant powder contains 3% to 15% of carbon blacks, MoSj, cr molybdenum dithiocarbamates (MoDTC), alone or ta combination.

[057] Preferably, the threaded tubular connection of the invention is such that at least one of the first and second passivation layers is coated with a barrier layer constituted by a minerai matrix layer comprising particles of silicon dioxide (SiCh).

[058] Preferably, the minerai matrix layer further comprises potassium oxide.

[059] Preferably, the threaded tubular connection of the invention is such that at least one ofthe first and second passivation layers is coated with a barrier layer constituted by an organo-mîneral matrix layer comprising particles of silicon dioxide (S1O3).

[060] Preferably, the threaded tubular connection of the invention is such that at least one of the first and second passivation layers is coated with a layer of dry lubricant.

[061] Preferably, the male end portion in accordance with the invention further comprises a first abutment and the female end portion further comprises a second abutment, the first and second abutments being capable of coming into contact with each other at the end of makeup.

[062] Preferably, the threaded tubular connection in accordance with the invention is such that the male and female end portions arc produced from steel.

DESCRIPTION OFTHE FIGURES [063] Figure 1 represents a close-up view of a coated surface ofa threaded tube end, in section along the longitudinal axis, in a first embodiment in accordance with the invention.

[064] Figure 2 represents a close-up view of a coated surface of a threaded tube end, in 10 section along the longitudinal axis, in a second embodiment in accordance with the invention.

[065] Figure 3 represents a close-up view of a coated surface ofa threaded tube end, ln section along the longitudinal axis, in a third embodiment in accordance with the invention.

[066] Figure 4 represents a close-up view ofa coated surface ofa threaded tube end, in section along the longitudinal axis, in a fourth embodiment in accordance with the invention.

[067] Figure 5 represents a close-up view of a coated surface of a threaded tube end, in section along the longitudinal axis, ln a fifth embodiment in accordance with the 20 invention.

[068] Figure 6 shows comparative photographs ofa threaded element in accordance with the invention and a prior art threaded element.

[069] Figure 7 shows a photograph of a threaded element in accordance with an embodiment ofthe invention.

EMBODIMENTS [070] The invention will be better understood from the following description which provides non-limiting explanations. It should be noted that the substrate onto which the variais layers in accordance with the invention are deposîted is preferably formed from steel and that the invention may equally be performed on a male as on a female end.

[071] The threaded portion of the invention systcmatically comprises a threading which extends over its outer or inner peripheral surface depending on whether the threaded portion is respectively male or female, and a first sealing surface on said peripheral surface, said first sealing surface being capable of producing metal-metal interférence with a corresponding second sealing surface belonging to a complementary threaded portion. The sealing surface is important in the threaded portion în accordance with the invention because, when coated in accordance with the invention, it provides a seal to gas and to liquid with the metal/metal contact. Preferably, the metal/metal contact is produced with an interférence.

[072] In the description below, the layers are deposited on at least the threading ofthe threaded portion in accordance with the invention and on the sealing surface.

[073J In accordance with the invention, a metallic layer wherein zinc (Zn) is the major element by weight will be deposited on the substrate of the tubular threaded portion, preferably formed from steel. The metallic layer in accordance with the invention is idcally deposited electrolytically. The principle of this type of deposit is summarized below. Apart from its mechanical strength, the major advantage of the metallic layer is its microstructural uniformîty. It should bc understood hère that “microstructural uniformîty” does not necessarily imply a monophase crystalline structure; în contrast. the reverse is true.

[074] ïn the context of the invention, the term “metallic layer” means a layer constitutcd by métal. Clearly, impurities may be présent, but preferably, the layer is exclus!vely metallic. The exclusively metallic layer ofthe invention has the advantage of having a microstructural uniformîty. In fact, under the optical microscope with a magnificatîon ofx500, the observed microstructure has a homogeneous appearance.

[075] In fact, both the mechanical strength and the microstructural uniformîty ofthe metallic layer are substantially greater than those of organic coatings which, furthermore, hâve poorer stability to température.

[076] Déposition by electrolysis is a technique used here to reduce metallic ions or oxides into pure mctals by applying an electric current density which may bc from l amp/dm² to 100 amp/dm² In the context of the invention. The electrolytic bath is at a température in the range 18°C to 50“C. Below 18°Q the efficiency of the bath is insufficient Above 50°C, the chemical components (for examplc addîtives) of the bath will be degraded. As an example, a method for depositing a metallic coating known as bufTer electrolysis may require very high currents at the high end ofthe range cited above.

[077] The clectrolytes are necessary in order to providc the electrical conductivity and may be aqueous solutions or mohen salts. A metallic layer wherein zinc (Zn) is the major element by weight may be deposited electrolytically; this is the technique used in the invention. Other metals such as copper or even nickel may also be deposited electrolytically.

[078] Electrolysis in an aqueous medium is carried out with a System of two électrodes composed of an anode and a cathode. Ion réduction occurs at the cathode and is defined as follows:

A/”* 4- ne~ <-> A·/ , where Mrepresents a métal and n is a whole number.

[079] In the case of electro-deposition, the cathode is the substrate onto whîch déposition occurs. In facL ideally, this is a steel in the case ofthe invention.

[080] At the anode, the reaction obtained is an oxidation of water to form gaseous dioxygen in accordance with the two équations below, depending on whether the medium is respectively acldîc or alkalinc:

(P 2H₂O —*Ο_2{χ} +4Zf* +4e or [081] Onc of the principal dlfTiculties with electrolysis in an aqueous medium is the compétition that exists between réduction ofthe metallic ions and réduction ofthe solvent at the cathode, defined by the réaction:

2ff₂O + 2e~ -+H_2ixi + 2OH‘ [082] In theory, the reactions which should take place are linked to the potentials of the électrodes which are themselves linked to each selected material, but experiments carried ouï in the context ofthe invention produced results which were difïicuk to predict In fact, the kinettcs ofthe réactions is complex.

[083] ïhc work Modem Electroplating, John Wiley & Sons, Inc, 5^Λ édition, p.285307, seetion 10 : Electrodeposition of zinc and zinc alloys, R. Winand, 2010 provides more details regardïng the electrolytic déposition of zinc or an alloy of zinc onto substrates.

[084] The déposition of a metallic layer wherein zinc (Zn) is the major element by weight in accordance with the invention onto the substrate, preferably steel, means that both the corrosion behaviour, the galling résistance and the mechanical strength ofthe assembly can be modified at the same time. The presence ofa deposit ofan alloy with an element other than zinc (Zn) as the major element, i.e. having the highest content by weight of the éléments of the alloy, is not désirable because the corrosion behaviour performances are such that the desired effect is not obtained. The thickness of the metallic layer wherein zinc (Zn) is the major element by weight is preferably in the range 4 to 20 pm. Below 4 ptn, the anti-corrosion effect is reduced because the layer runs the risk of exhibiting insufïicicnt corrosion behaviour. Above 20 pm, there îs a high risk ofthe accumulation ofby combination ofH* in accordance with équation ( I ). This accumulation is higher when the layer Is thicker. There is then the danger that Ha gas will be trappcd in the structure, which will become more fragile due to the génération of internai stresses. Still more preferably, the thickness ofthe metallic layer is in the range 6 to 15 pm.

[085] The metallic layer wherein zinc (Zn) is the major element by weight, deposited electrolytically, may be completed by additional treatments such as the formation of a passivation layer on the metallic layer. In a variation, it is also possible to deposit, over the whole ofthe metallic layer orover a portion thereof a lubricant layer comprising a resin and a dry solid lubricant powder dispersed In this resin. In addition to its lubricatîng function, this layer may contribute to the anti-corrosion function. It is entirely possible in the context ofthe invention to deposit a lubricant layer of this type on the passivation layer. The lubricant layer has a thickness in the range 5 pm to 50 pm. Below 5 pm, the hibricatlng effect is not satisfactory. Above 50 pm, the maximum makeup torque may become too high. Furthermore, above 50 pm, there Is the danger that chips originatîng from the damaged coating might be formed. Chips ofthis type might fai! to the bottom of the oîl well and consequently cause the operating conditions to deteriorate. Preferably, the fabricant layer has a thickness in the range 10 pm to 30 pm.

[086] Other variations consist of depositing a barrier layer generally known as a sealer onto the formed passivation layer.

[087] Another variation also consists of depositing a fabricant layer on the entire passivation layer which has been formed, or onto just a portion thereof.

[088] It is also entirely possible to deposit a fabricant layer, with or without an anticorrosion function, onto the metaliic layer in its entirety or onto just a portion thereof without having formed a passivation layer.

[089] The various layers in the various configurations of the invention are deposited by means of successive operations carricd out on the preferably metaliic substrate, or even more preferably onto steel. The following operations arc carricd out: chemical or electrochemical degreasing of the substrate using solvents and/or alkaline solutions, followed by rinsîng. Next, chemical or electrochemical stripping of the surface of the substrate is carried out, preferably by immersîng the substrate in an acidic solution in order to elimînate the surface oxides.

[090] The surface may bc activated using the following products: hydrochloric acid, sulphurîc acid, phosphoric acid, nitric acid, hydrofluoric acid or a mixture of these acids.

[091] !n accordance with the invention, a metaliic layer wherein zinc (Zn) is the major element by weight is deposited onto the threaded end portion comprising a threading and a first sealing surface. This means that the deposit ofthe metaliic layer, Ideally carried out by elcctrolysis, may be.* zinc (Zn) alone or a binary alloy of zinc (Zn) of the type Zn-X, in which X is selected from nickel (Ni), iron (Fe), magnésium (Mg) and manganèse (Mn).

[092] Pure Zn will be used for its anti-corrosion and anti-galling characteristics. In accordance with the invention, a metaliic layer wherein zinc (Zn) is the major eicment by weight is used because, compared with iron, in the context of a steel type substrate, zinc has a more négative standard potential. In other words, Zn offers effective cathodic protection against corrosion in this case.

[093] In the context of a steel type substrate, using pure Zn is thus not problematic, but Ζπ-Ni îs preferred because pure Zn îs consumed (chemically eroded) at a higher rate. Thus, a particularly thlck layer would be roquired, which is not advantageous on the threading and the sealing surface. In fact, a thick layer would resuit in a smaller clearance at the threads, which would impair optimization of the contact surfaces which would be preferred to be made, depending on the type of connection. Zn-Ni should be used, not just for its anti-corrosion characteristics, but also for its anti-galling characteristics.

[094] Zn-Fc is also a sacrîficial protection as regards the preferred steel type substrate. The layer of Zn-Fe is a good adhesion promoter. Zn-Fe produces a lower corrosion rate than pure Zn.

[095] Zn-Mg is of interest, because this alloy slows down the rate of corrosion due to the presence of Mg in the case ofa preferred substrate, Le. steel.

[096] ïn the context of a steel type substrate, Zn-Mn provides barrier protection. However, the barrier function is of advantage in tenus of anti-corrosion résistance because it will not be attacked and will romain intact. Furthermore, it has vay good corrosion behaviour when naturally exposed.

[097] It will be rccalled that electrolytîc déposition can be used to improve the uniformity of the deposit from a mïcrostructural viewpoint Clearly, other manners of deposittng a metallic coating exist, such as galvanization, spraying. or even sherardizing.

[098] The alternative, consisting of forming a passivation layer on the metallic layer, means that the corrosion résistance can be further improved.

[099] The alternative, consisting of depositing a lubricant layer comprising a resin and a dry solid lubricant powder dispersed in said resin over at least a part of the portion, means that the makeup torque of the connection can be better controlled and galling can be avoided.

[0100] The dry solid lubricant powder is preferably selected from the group constituted by polytetrafluoroethylcncs (PTFE), molybdenum disulphldes (MoSj), carbon blacks (C), graphite fluorides (CF_X) or a mixture thereof.

[0101] PTFEs (polytetrafluoroethylenes) provide lubricating properties with a coefficient of friction which is stable with contact pressure. The makeup torque is thus better controlled. The mean particle size ofthe PTFE particles ofthe invention îs less than 15 gm. Above 15 gm, the dispersion in the resin would be heterogeneous because the 5 part icles would be too thîck compared with the total thickness ofthe fabricant layer.

[0102] The resin is selected from the group constituted by polyvinyl restas, epoxy resins, acrylic restas, polyuréthane restas and polyamide-imidc restas.

[0103] The polyvinyl resins, epoxy resins and acrylic resins adhère in a satisfactory manner to the mctallic layer containing Zn or the passivation layer.

[0104] Polyuréthane resins hâve the advantage of being particularly stable chemically and are easy to employ by curing.

[0105] Polyamide-imide restas are particularly résistant to wear.

[0106] ln a preferred embodiment, the resin is acrylic in type and the dry solid fabricant powder dispersed in said resin contains 3% to 15% of carbon blacks, M0S2, or 15 molybdenum dithîocarbamates (MoDTC), alone or fa combination. This combination exhlbits a synergistic effect fa terms of anti-galling, adhesion and control ofthe makeup torque.

[0107] The molybdenum disulphides (M0S2), molybdenum dithîocarbamates (MoDTC), carbon blacks (C), graphite fluorides (CF,) or a mixture thereof supply 20 lubricating properties with a coefficient of friction which is stable with contact pressure.

The makeup torque is thus better controlled. .

[0108] Dérivatives of M0S1 also hâve ail of the lubricating properties cited above.

[0109] ln a preferred embodiment the deposîted layers of métal containing Zn are a binary Zn-NÏ alloy containing between 12% and 15% ofNi, the remainder clearly being 25 Zn and inévitable impurities wherein the sum of the quantifies is strictly less than 3% by weight ln fact, below 12% ofNi, the corrosion résistance is not optimized, while above 15% of nickel, the structure ofthe coating is no longer monophase but polyphasé, and the phases présent taduce interna! stresses and render the coating fragile.

[0110] Finally, the microstructure ofthis preferred metallic deposit ofZn-Ni with 12% 30 to 15% ofnickel is preferably ofthe monophase type and the phase which is présent is gamma in type. This gamma type crystalline structure ensurcs better corrosion résistance.

[0111] Preferably, the passivation layer comprises trivalent chromium Cr(lII). This trivalent chromium îs more stable than Cr(U) and not harmfùl to health, unlikc Cr (VI).

[0112] Preferably, the passivation layer, when it is présent, is coated with a barrier layer constituted by a minerai matrix layer comprising particles of silicon dioxide (SiOJ. This barrier layer Împroves the anti-corrosion résistance.

[0113] An alternative consists of using a passivation layer coated with a barrier layer constituted by an organo-mineral matrix layer comprising particles of silicon dioxide (SiOj). This barrier layer împroves the anti-corrosion résistance.

[0114] One embodiment consists of depositing a lubricant layer onto the passivation layer in order to better control the makeup torque of the connection and to avoid galling. [0115] The metal/metal contact of the threaded portions of the invention is made with an interférence. The “interférence between the male and female éléments of the invention corresponds to a diametrical interférence between coupled points of the two surfaces of révolution. More particularly, this diametrical interférence is defined by the différence in the diameter ofthe regular section ofthe surfaces at the coupled points ofthe two surfaces of révolution. This différence may be measured before assembling said cléments, then may be evaluated at the contact surface when the two éléments hâve been assembled with each other. In practice, it is a routine matter to ensure that one diameter of a portion of the outer peripheral surface of the male element is slightly greater than the diameter of a portion of the inner peripheral surface ofthe female element This brings about an exchange of material in the contact zone of these surfaces. Thus, a high contact pressure is provided between said coupled points.

EXAMPLES [0116] The non-limiting examples of threaded portions (either male or female or both) formed from steel described below were treated clectrolytically with a binary zinc-nickel allô y. The binaiy zinc-nickel alloy used ln the examples is available from ELECTROPOLI (rcgïstercd trade mark) under the commercial name ZELTEC 2.4 (registered trade mark). , [0117] The parameters for the electrolytic treatment were as follows:

- température of electrolytic bath: Temp. 36°C ;

- pH of electrolytic bath: pH ^e 5.4 ;

- applied current density: J “ 2 A/dm³ ;

- dwell time in electrolytic bath: t - 20 min.

[0118] Thus, the electrolytic treatment was carried out in an acidic medium.

[0119] This produced a metallic layer comprising zinc (Zn). The thickness of the metallic layer was în the range 4.0 pm to 12.5 pm (extreme values), typically 6 pm to approximately 8 pm. The nickel (NI) content was generally in the range 12% to 15% (extreme values). It followed that the zinc (Zn) content was generally in the range 85% to 88% (extreme values). The metallic layer had both anti-galling and anti-corrosion properties.

[0120] When a barrier layer was présent, it was in particular the product sold under the name FINIGARD 460 from COVENTYA (registered trade mark).

[0121] When a passivation layer was présent, it was în particular the product sold under the name FINID1P 128 CF (cobalt free) from COVENTYA (registered trade mark). It could also be the product sold under the name EcoTrî (registered trade mark) NoCo from ATOTECfi (registered trade mark) Deutschland GmbH. These two products hâve the particular advantage of being free of hexavalent chromium (Cr(Vl)).

[0122] In the exemplary embodiments described below, each threaded portion is intended to form a portion of a threaded tubular connection. Each threaded portion has an axis of révolution and comprises a threading. The threading extends over the outer peripheral surface of the threaded portion when it is a male element; tn contrast, the threading extends over the inner peripheral surface of the threaded portion when h is a female element. Each threaded portion also comprises a first scaling surface on the peripheral surface which is arranged to produce metal-metal interférence tvith a corresponding second sealing surface befonging to a complementary threaded portion of a tube. A complementary threaded portion of a male portion Is a female threaded portion. A complementary threaded portion ofa female portion is a male threaded portion.

[0123] In the exemplary embodiments below, reference is systematically made to an assembly of two complementary threaded portions which can form a tubular connection when they are made up one into the other. It should be understood that the surface treatments, the layers and the fuiishing treatments may be applied inespectivcly to a male threaded portion or to a female threaded portion. As a conséquence, when an embodiment makes reference to a male portion comprising a certain particular first coating (ensemble of layers) and makes reference to a female portion comprising a certain particular second coating (other ensemble of layers), it should be understood that it is possible to reverse the particular first and second coatings ofthe threaded portions, Le. apply the first particular coating to the female portion and apply the second particular coating to the male portion. EXAMPLE I [0124] Figure 1 shows a substrate 100 formed from steel. The substrate 100 is shaped so as to form a female threaded portion 102 and a male threaded portion 104.

[0125] The male threaded portion 104 is coated with a first anti-corrosion and antigalling layer 108. The first metallic layer 108 Is deposited electrolytically, as described above. The first metallic hyer 108 is constituted by a binary zinc-nickel (Zn-Ni) alloy and contains zinc (Zn), namely in a mean amount of 85.7%. The first metallic layer 108 has a mean thickness of 83 pm. Furthermorc, the first metallic layer has a monophase gamma type microstructure.

[0126] The first metallic layer 108 is coated with a passivation layer 110, as described above. By définition, the passivation layer has anti-corrosive properties.

[0127] Optîonally, the passivation layer 110 is coated with a barrier layer 114 as described above, which also has anti-corrosive properties.

[0128] The female threaded portion 102 is coated with a second metallic anti-galling layer 106. The second metallic layer 106 is constituted by a binary Zn-Ni alloy.

[0129] The second metallic layer 106 is deposited electrolytically. The second metallic layer 106 contains mainly zinc (Zn) by weight. Furthermorc, the second metallic layer has a monophasé gamma type microstructure.

[0130] The second metallic layer 106 is coated with a lubricant layer 112. In the embodiment of Figure I, the lubricant layer 112 is of the hot-melt type, having both lubricating properties and anti-corrosive properties.

[0131] The hot-melt lubricant layer has the following composition by weight: matrix: 70% to 95% solid lubricant: 5% to 30%.

The matrix has the following composition: 18450 homopolymeric polyethylene: 8% to 90% camauba wax: 5% to 30% zinc stéarate: 5% to 30% calcium sulphonate dérivative: 0 to 50% alkyl polymethaciylate: 0 to 15% colorant: 0 to 1% antioxidant: 0 to 1%

Silicone (surfactant element): 0 to 2%

EXAMPLE 2 [0132] Figure 2 shows a substrate 100 formed from steel. The substrate 100 is shaped so as to form a female threaded portion 102 and a male threaded portion 104.

[0133] The male threaded portion 104 is coated with a metallic anti-corrosion and antigalling layer 108. The metallic layer 108 is deposited electrolytically, as described above. The metallic layer 108 is constituted by a binary zinc-nickcl (Zn-Ni) alloy and contains zinc (Zn), namely a mean amount of 86.5%. The first métal layer 108 has a mean thickness of 6.7 pm.

[0134] The metallic layer 108 of the male threaded portion 104 is coated with a passivation layer 110, as described above. By définition, the passivation layer has anticorrosive properties.

[0135] The passivation layer 110 ofthe male threaded portion 104 is coated with a barrier layer 114 as described above, which also has anti-corrosive properties.

[0136] The female threaded portion 102 is coated with a metallic anti-corrosion and anti-galling layer 108. The metallic layer 108 is deposited electrolytically, as described above. The metallic layer 108 is constituted by a binary zinc-nickel (Zn-Ni) alloy and contains zinc (Zn), namely a mean amount of 86.4%. The metallic layer 108 has a mean thickness of 7.4 pm.

[0137] The metallic layer 108 of the female threaded portion 102 is coated with a passivation layer 110, as described above. By définition, the passivation layer has anticorrosive properties.

[0138] The passivation layer 110 ofthe female threaded portion 102 is coated with a fabricant layer 112. [n the embodiment ofFigure 2, the fabricant layer 112 is ofthe hotmelt type having both fabrîcating properties and anti-corrosive properties.

EXAMPLE 3 [0139] Figure 3 shows a substrate 100 formed from steel. The substrate 100 is shaped so as to form a female threaded portion 102 and a male threaded portion 104.

[0140] The male threaded portion 104 is coated with a metallic anti-corrosion and anti-galling layer 108. The metallic layer 108 has been deposited electrolytically, as described above. The metallic layer 108 is constituted by a binary zinc-nickel (Zn-Ni) alloy and contains zinc (Zn), namely a mean amount of 86.5%. The first metallic layer 108 has a mean thickness of 7 pm.

[0141] The metallic layer 108 of the male threaded portion 104 is coated with a passivation layer 110, as described above. By définition, the passivation layer has anticorrosive properties.

[0142] The passivation layer 110 ofthe male threaded portion 104 is coated with a barrier layer 114 as described above, which also has anti-corrosive properties.

[0143] The substrate 100 ofthe female threaded portion 102 has a surface roughness. The surface roughness has been obtained by a sand blasting process. A sand blasting process in particular enabled a surface roughness (Ra) in the range 1.0 pm to 10 pm to be produced. In the exemplary embodiment of Figure 3, the surface roughness (Ra) is approximately 2 pm.

[0144] The female threaded portion 102 is coated with a metallic anti-corrosion and anti-galling layer 108. The metallic layer 108 has been deposited electrolytically, as described above. The metallic layer 108 is constituted by a binary zinc-nickel (Zn-Ni) alloy and contains zinc (Zn), namely a mean amount of 85.6%. The metallic layer 108 has a mean thickness of 7 pm.

[0145] The metallic layer 108 ofthe female threaded portion 102 is coated with a passivation layer 110, as described above. By définition, the passivation layer has anttcorrosivc properties.

[0146] The passivation layer 110 ofthe female threaded portion 102 is coated with a fabricant layer 112. In the embodiment of Figure 3, the fabricant layer 112 comprises a resin and a dry solid fabricant dispersed in this resin. In this case, the fabricant layer 112 is constituted by a polyuréthane resin (type PU2K) în which particles of carbon black hâve been dispersed.

EXAMPLE 4 [0147] Figure 4 shows a substrate 100 formed from steel. The substrate 100 is shapcd so as to form a female threaded portion 102 and a male threaded portion 104.

[0148] The male threaded portion 104 is coated with a metallic anti-corrosion and anti-galling layer 108. The metallic layer 108 has been deposîted electrolytically, as described above. The metallic layer 108 is constituted by a binary zinc-nickel (Zn-Ni) alloy and contains zinc (Zn), namely a mean amount of 86.3%. The first metallic layer 108 has a mean thickness of 73 pm.

[0149] The metallic layer 108 ofthe male threaded portion 104 is coated with a passivation layer 110, as described above. By définition, the passivation layer has antîcorrosive properties.

[0150] Optionally, the passivation layer 110 ofthe male threaded portion 104 is coated with a barrier layer 114 as described above, which also has anti-corrosive properties.

[0151] The substrate 100 of the female threaded portion 102 has a surface roughness. The surface roughness has been obtained by a sand blasting process. In the exemplary embodiment of Figure 4, the surface roughness (Ra) is approximately 2 pm. In a variation, the sand blasting process may be carried out on the metallic antj-corroslon and anti-galling layer 108 ofthe female threaded portion 102 described below.

[0152] The female threaded portion 102 is coated with a metallic anti-corrosion and anti-galling layer 108. The metallic layer 108 has been deposîted electrolytically; as described above. The metallic layer 108 îs constituled by a binaiy zinc-nickel (Zn-Ni) alloy and contains zinc (Zn), namely a mean amount of 86.8%. The metallic layer 108 has a mean thickness of 7.7 pm.

[0153] As mentioned above, a sand blasting process may be carried out on the metallic layer 108 of the female threaded portion 102. In one embodiment of the invention, the metallic layer 108 has a surface roughness (Ra) of approximately 2 pm. This means that the passivation layer or the lubricant layer 112 described below can adhéré well.

[0154] The metallic layer IÛ8 of the female threaded portion 102 is optionally coated with a passivation layer 110, as described above. By définition, the passivation layer has anti-corrosive properties.

[0155] The passivation layer 110 ofthe female threaded portion 102 is coated with a fabricant layer 112. In the embodiment of Figure 4, the fabricant layer Is constituted by epoxy and MoS;.

[0156] In a variation, it is possible for there to be no passivation layer 110 and to apply the fabricant layer 112 dircctly to the metallic layer 108 ofthe female threaded portion 102 (or directly to the metallic layer 108 ofthe male threaded portion as appropriate).

EXAMPLE 5 [0157] Figure 5 shows a substrate 100 formed from steel. The substrate 100 is shaped so asto form a female threaded portion 102 and a maie threaded portion 104.

[0158] The substrate 100 of the male threaded portion 104 has a surface roughness. The surface roughness has been obtained by a sand blasting process. In the exemplary embodiment of Figure 5, the surface roughness (Ra) is approximately 2 pm. In a variation, the sand blasting process may be carried out on the metallic anti-corrosion and anti-galling layer 108 ofthe female threaded portion 102 described below.

[0159] The male threaded portion 104 is coated with a metallic anti-corrosion and anti-galling layer 108. The metallic layer 108 has been deposited clcctrolytically, as deseribed above. The metallic layer 108 is constituted by a binary zinc-nickel (Zn-Ni) alloy and contains zinc (Zn), nameiy a mean amount of 86.7%. The mctaüic layer 108 has a mean thickness of 7.2 pm.

[0160] As mentîoned above, a sand blasting process may be carried out on the metallic layer 108 of the male threaded portion 104. In one embodiment of the invention, the metallic layer 108 has a surface roughness (Ra) of approximately 2 pm. This means that the passivation layer or the fabricant layer 112 described below can adhéré well.

[0161] The metallic layer 108 of the male threaded portion 104 is optionally coated with a passivation layer 110, as described above. By définition, the passivation layer has anti-corrosive properties.

[0162] The passivation layer 110 ofthe male threaded portion 104 is coated with a fabricant layer 112. In the embodiment of Figure 5, the fabricant layer 112 is constituted by acryüc resin and carbon black [0163] In a variation, it is possible for there to be no passivation layer 110 and to apply the lubricant layer 112 directly to the métal lie layer 10S of the male threaded portion 104.

[0164] The substrate 100 ofthe female threaded portion 102 has a surface roughness. The surface roughness has been obtained by a sand blasting process. In the exemplary embodiment of Figure 5, the surface roughness (Ra) is approximately 2 pm. In a variation, the sand blasting process may be carried out on the metallic anti-corrosion and anti-gallîng layer 108 ofthe female threaded portion 102 described below, [0165] The female threaded portion 102 is coated with a metallic anti-corrosion and anti-galling layer 108. The metallic layer 108 has been deposited clectrolytically, as described above. The metallic layer 108 Is constituted by a binary zinc-nickel (Zn-Ni) alloy and contains zinc (Zn), namely a mean amount of 86.2% by weight The metallic layer 108 has a mean thickness of 6.7 pm.

[0166] As mentioned above, a sand blasting process may be carried out on the metallic layer 108 ofthe female threaded portion 102. In one embodiment ofthe invention, the metallic layer 108 has a surface roughness (Ra) of approximately 2 pm. This means that tbe passivation layer or the lubricant layer 112 described below can adhère well.

[0167] The metallic layer 108 of the female threaded portion 102 is optionally coated with a passivation layer 110, as described above. By définition, the passivation layer has anti-corrosive properties.

[0168] The passivation layer 110 ofthe female threaded portion 102 is coated with a lubricant layer 112. In the embodiment of Figure 5, the lubricant layer 112 is constituted by an acrylic resin and a dispersion of carbon black in that resin.

[0169] In a variation, it is possible for there to be no passivation layer 110 and to apply the lubricant layer 112 directly to the metallic layer 108 of the female threaded portion 102 (or directly to the metallic layer 108 of the male threaded portion, as appropriate).

[0170] In particular embodiments, at least some of the layers may extend over other éléments ofthe threaded portion. As an cxample, when an abutment is présent on the threaded portion, the layers may extend over it.

[0171] The Applicant has carried out comparative roughness tests between threaded portions before eiectrolytic déposition of a metallic layer in accordance with the invention and after electrolytic déposition of a metallic layer in accordance with the invention. The roughness was measured in the direction parallel to the direction of machining of said portions. The results are reported în Table 1.

	Before electrolytic déposition ZnNi	After electrolytic déposition ZnNi
Roughness	Ra(gm)	Rz(gm)	Rt(gm)	RaQun)	Rz(gm)	Rt(gm)
No sand blasting	Mean	0.458	2.453	2.453	0.330	2.023	4.316
StdDev	n.a.	n.a.	n.a.	0.166	0.569	3.895
Sand blasting	Mean	3.254	21243	21243	i.495	9.918	11.561
Std Dev	0.171	1271	1271	0.166	1.127	2.060

Table 1. Comparison of roughness. Std Dcv = standard déviation n.a. ^Bnot applicable [0172] Ra is the mean déviation roughness- it is the arithmetic mean ofthe absolute values of the distances between the peaks and valleys measured on the roughness profile. Rz is known as the mean maximum roughness - this is the mean of the maximum heights measured over several (for examplc 5) selected portions on a roughness profile. Rt is known as the total roughness — this is the maximum height measured over the whole ofthe roughness profile.

[0173] Table 1 shows that the samples ofthreaded portions after electrolytic déposition hâve a reduced roughness în the direction parallel to the direction of machining compared with the samples of threaded portions before electrolytic déposition. In particular, the electrolytic déposition in accordance with the invention has a levelling effect.

[0174] Figure 6 shows photographs of threaded cléments taken with an optïcal microscope. More particularly, Figure 6 shows two selected portions of a prior art threaded element compared with two analogous selected portions of a threaded element in accordance with the invention.

[0175] The microscope used was optical. The magnification was: x500. The scale indicated on each photograph is 50 gm.

[0176] The prior art threaded élément is shown in photographs 200a and 200b. The prior art substrate 202 formed from steel is coated with a layer 204 comprising particles of lamdlar zinc dispersed in an epoxy resin. The layer 204 was applied using a process whîch îs known în the art. The prior art process comprises pneumatic spray ing of the layer 204 onto the substrate 202 at ambient température, followed by hot curîng ofthe substrate/layer ensemble. During the spraying phase, the composition of the layer 204 comprises a solvent The curing phase is used to eliminate the solvent and cross-link the layer 204. The photographs 200a and 200b show that the layer 204 is heterogeneous. In fact, the layer 204 ofthe prior art threaded element has a non-uniform mrcrostructure.

[0177] The threaded element of the invention îs shown in photographs 300a and 300b. The substrate 100 is coated with a first metallic layer 108 constituted by a binary Zn-Ni alloy of the type described in Example I above. The binary alloy was applied electrolytically in order to form a homogeneous layer. In fact, photographs 300a and 300b ofFigure 6 show that the first metallic layer 108 ofthe threaded element ofthe invention has a uniform microstructure. In the présent case, it îs a monophase gamma (γ) type microstructure.

[0178] Figure 7 shows a photograph 400 of a threaded element in accordance with the invention taken with an optical microscope. The magnification is: x500. The scale indicated on each photograph is 50 pm.

[0179] The substrate 100 was coated with a second metallic layer 106 constituted by a binary Zn-Ni alloy of the type described in Example I above. The binary alloy was applied electrolytically in order to form a homogeneous layer. The metallic layer had a thickness of approximately 4 pm to approximately 6 pm (mean thickness approximately 5 pm). The metallic layer was coated with a fabricant layer 112 of the hot-melt HMS-3 type, as described in Example I. The fabricant layer has a thickness ofapproximately 40 pmto approximately 43 pm.

[0180] The second metallic layer 106 has a uniform microstructure. In fact, the second metallic layer constituted by a binary Zn-Ni alloy also has a monophasé gamma (γ) type mrcrostructure.

[0181] Figures 6 and 7 thus demonstrate that the metallic layer of the invention has a uniform microstructure.

[0182] The éléments of the tubes of the invention, namely the male or female threaded portions as well as the connections produced with these portions, comply with the conditions of international standard API RP 5C5 (3^Μ Edition, July 2003). In particular, the tube cléments resisted 15 makeup/breakout procedures and fiilly satisfied the sealing 5 conditions.

[0183] The éléments ofthe tubes ofthe invention, namely the male or female threaded portions as well as the connections produced with these portions, were in fùll compliance with the conditions of European standard NF EN ISO 9227 relating to saline mist tests. In particular, the tube éléments responded positive ly as regards corrosion résistance over 10 1000 h of exposure to an aggressive environment

Claims (15)

1. A threaded portion of a tubular element for a threaded tubular connection having an axis of révolution, said portion comprising a threading extending over its outer or inner peripheral surface, and a first sealing surface on said peripheral surface, said first sealing surface being capable of producing metal-metal interférence with a corresponding second sealing surface belonging to a complementary threaded portion of a tube, characterized in that said threading and said first sealing surface arc coated with a metaliic anti-corrosion and anti-gailing layer wherein zinc (Zn) is the major element by weight

2. The threaded portion according to claim 1, in which the metaliic anti-corrosion and anti-galling layer is deposited electrolytically.

3. The threaded portion according to one of the preceding claims, in which the metaliic anti-corrosion and anti-galling layer contains at least 50% by weight of zinc (Zn).

4. The threaded portion according to onc of the preceding claims, in which the metaliic anti-corrosion and anti-galling layer has a thickness in the range 4 pm to 20 pm.

5. The threaded portion according to onc of the preceding claims, in which the metaliic anti-corrosion and anti-galling layer comprises a substance selected from the group constituted by pure zinc (Zn) and a binary alby of zinc (Zn) of the type Zn-X, in which X is selected from nickel (Ni), iron (Fe), magnésium (Mg) and manganèse (Mn).

6. The threaded portion according to claim 5, in which the metaliic anti-corrosion and anti-galling layer is a zinc-nickel (Zn-Ni) alloy wherein the nickel (Ni) content is in the range 12-15% by weight and wherein the microstructure is monophase and in the gamma (y) phase.

7. The threaded portion according to one of claims 1 to 6, in which said the metaliic anti-corrosion and anti-galling layer is coated with a fabricant layer comprising a resin and a dry solid fabricant powder dispersed in said resin.

8. The threaded portion according to daim 7, in which said metaliic anti-corrosion and anti-galling layer is coated with a passivation layer comprising Vivaient chromium (Cr(ni)), said passivation layer being formed between the metallic layer and the lubricant layer.

9. The threaded portion according to one of daims I to 6, in which said metallic anti-corrosion and anti-galling layer is coated with a passivation layer comprising trivalent chromium (CrfHI)).

10. The threaded portion according to claim 9, in which the passivation layer is coated with a barrier layer constituted by a minerai matrix layer comprising particles of silîcon dioxide (SiOi).

11. The threaded portion according to claim 9, in which the passivation layer is coated with a barrier layer constituted by an organo-mtneral matrix layer comprising particles of silicon dioxide (SiOi).

12. The threaded portion according to one of the preceding daims, in which said portion further comprises a first abutment which is capable of coming into contact with a corresponding second abutment, at the end of makeup, belonging to a complcmentary threaded tube portion.

13. The threaded portion according to one of the preceding daims, in which said threaded portion is produced from steel.

14. The threaded portion according to one ofthe preceding daims, in which said portion ïs male in type, with a threading extending over its outer peripheral surface as weil as a first sealing surface on said outer peripheral surface.

15. The threaded portion according to one of the preceding daims, in which said portion ïs female in type, with a threading extending over its inner peripheral surface as weil as a first sealing surface on said inner peripheral surface.