Chassis with static sealing points

Description

Technical Field

[0001] The invention relates to the field of aircraft landing gear and more specifically to the materials used for the latter as well as the methods for obtaining them. Prior art

[0002] An aircraft landing gear is a component comprising a wheel, and enabling the aircraft to be supported during taxiing, takeoff or landing phases. Such a landing gear generally comprises a rod which must be sufficiently rigid to support the aircraft, and is generally equipped with a damping system enabling the landing gear to accommodate the mechanical stresses exerted on the wheel during takeoff and landing stages.

[0003] Existing damping systems typically include a piston that moves in a chamber filled with a viscous fluid. This slows the piston's movement and cushions the landing gear to which it is connected.

[0004] Examples of prior art landers are described in US2007 / 164151 A1, EP3112263 A1 and EP3112262 A1.

[0005] In order to avoid any loss of fluid and to ensure proper functioning of the damping systems, it is necessary to ensure the sealing of the damping systems and this is why the damping systems have static sealing points.

[0006] Currently, these static sealing points comprise substrates coated with chrome or nickel sandwiching seals made of elastically deformable material. However, the coatings currently considered do not have sufficient characteristics for other aspects essential to landing gear parts, including good corrosion resistance, and this is why static sealing points are today composed of several superimposed coatings to be able to guarantee a satisfactory performance package. This results in a complex preparation of landing gear parts. Furthermore, chrome coatings are affected by legislative changes that require their replacement in the coming years, because the use of chrome presents dangers to the environment and to humans.

[0007] There is therefore a need for the development of new materials suitable for static sealing points of landers which would be free from the disadvantages of the materials currently used. Statement of the invention

[0008] In order to meet this need, the inventors propose a landing gear according to claim 1.

[0009] The inventors have found that steel sealing points with zinc and nickel alloy coatings having a surface roughness Ra as indicated above, allows the production of static sealing points ensuring static sealing characteristics at least identical, if not superior to the static sealing points of the prior art. In addition, the materials used are free from the disadvantages associated with the use of the materials of the static seals of the prior art, and are in particular more environmentally friendly.

[0010] It is understood that the surface roughness Ra of a part should be understood as the average surface roughness within the meaning of ISO 4288. For example, this roughness can be measured by the stylus method. In this method, the roughness of a surface is determined by moving a probe tip at a constant speed over the surface of a part.

[0011] Furthermore, the inventors have found that, in addition to allowing the replacement of prior art coatings, made of chrome or nickel, the coatings of the invention made of zinc and nickel alloy make it possible to ensure other essential characteristics for landing gear parts. In particular, the zinc and nickel alloy coatings provide anti-corrosion properties comparable to, if not superior to, those of the prior art coatings.

[0012] The nickel content of between 12 and 18% ensures that the alloy is in the gamma phase, which ensures that the coating has the desired properties. In addition, this crystallographic phase of the coating ensures, in addition to the low roughness obtained, good anti-corrosion properties.

[0013] Thus, in addition to ensuring good static sealing at the static sealing point, zinc and nickel alloy coatings allow a single coating composition to be used more widely in the lander for several functions and thus greatly simplify the manufacturing processes of the lander. It is understood that "static" sealing is understood as the sealing between two parts that are not moving relative to each other.

[0014] In particular, the static sealing of the at least one static sealing point is understood as a static gas seal and a static hydraulic fluid seal.

[0015] In one embodiment, the zinc and nickel alloy coating has a thickness of between 10 and 30 µm.

[0016] In one embodiment, the zinc and nickel alloy coating comprises, as a mass percentage of the alloy, between 12% and 16% of nickel, at most 0.5% of elements other than nickel, the remainder being zinc.

[0017] In one embodiment, the seal made of elastically deformable material is composed of one or more materials chosen from: polybutadiene, chlorinated polyethylene, chloroprene, chlorosulfonated polyethylene, fluorocarbons, fluorosilicones, hydrogenated nitriles, polyacrylates, perfluoroelastomers, polyacrylates, polyurethanes, silicone and its derivatives, or from nitrile-butadiene, ethylene-propylene, ethylene-acrylate, isobutylene and isoprene, styrene-butadiene, tetrafluoroethylene and propylene copolymers.

[0018] Furthermore, the shape of the seal is not decisive for obtaining the effect described above. The seal can thus be chosen from the seal shapes necessary for the proper implementation of the invention. In particular, the seal can be round, toric, “T” shaped, of square section or even of hexagonal section.

[0019] In one embodiment, the static sealing area may further comprise one or more rings of a more rigid material, disposed around the seal, and extending between the first and second surfaces.

[0020] Such rings protect the elastically deformable material when the sealing area is subjected to high pressure differences. For example, these rings can be made of polyethylene terephthalate, nylon or polyetheretherketone. Such rings can also ensure that even when the static sealing area is subjected to high pressure differences, the seal made of elastically deformable material does not stretch into the gaps that may exist between the first and second surfaces.

[0021] In one embodiment, at least one of the surfaces of the first and second parts may comprise an organo-mineral layer on and in contact with the zinc-nickel alloy coating.

[0022] Such an organo-mineral layer allows to ensure a roughness of the surface of the part even lower than that obtained in the absence of the organo-mineral layer. However, such a layer is not necessary to obtain the desired static sealing characteristics, provided that the average roughness Ra of the surface of the part of the nickel and zinc alloy coating is less than or equal to 1.6 µm.

[0023] In one embodiment, only one of the surfaces of the first or second parts of the lander comprises an organo-mineral layer.

[0024] In one embodiment, the surfaces of the first or second parts of the lander comprise an organo-mineral layer.

[0025] In one embodiment, neither surface of the first or second parts of the lander comprises an organo-mineral layer.

[0026] It is understood that an organo-mineral layer comprises an organic part and / or a mineral part.

[0027] In one embodiment, the organo-mineral layer may be selected from a silicone-based organo-mineral layer or an aluminum-rich organo-mineral layer.

[0028] Where applicable, the organic part and the mineral part form a single layer, that is to say that the two parts are mixed within the same layer and do not appear as two separate layers.

[0029] In one embodiment, the organo-mineral layer may comprise an organic portion comprising ethoxylated alcohols and an inorganic portion comprising a silicic acid.

[0030] In other embodiments, the organo-mineral layer may be an epoxy resin.

[0031] Other types of organo-mineral layers can also work provided that they achieve the desired effect, namely to further reduce the surface roughness of the first or second part.

[0032] The organo-mineral layer may or may not include a lubricant.

[0033] To facilitate its application, the organo-mineral layer can be chosen from water-soluble agents or it can be used diluted in a solvent.

[0034] In a preferred embodiment, the organo-mineral layer is chosen to be water-soluble, and comprises an inorganic and organic component and with integrated lubricant.

[0035] In one embodiment, the steel substrate of the first and second parts of the landing gear may be made of a steel selected from the following steels: 35NCD16, 35CD4, 35NC6, S99, S154, 25CD4S, Z8CND17-04, Z6CNU17-04, Z15CN17-03, S143, S144, S145, Z2CN18-10, Z2CN18-10 / Z3CN18-10, Z10CNT18-10, Z12CNT18-10, XES, XC18S, 17-4PH, X2CrNi 18-9, 304L, Z6CNT18, 17-7PH, DC04 or C22E / R.

[0036] According to another of its aspects, which is not covered by the claims, the invention also relates to a method for obtaining a part comprising a steel substrate coated with a zinc and nickel alloy coating, comprising in mass percentage of the alloy between 12% and 18% and nickel, at most 0.5% of elements other than nickel and zinc, the remainder being zinc, the surface of which has an average roughness Ra less than or equal to 1.6 µm comprising at least the following steps: a step of degreasing the substrate; a step of preparing the substrate; a step of electrolytic deposition of the coating by dipping the substrate in an alkaline bath comprising a nickel sulfate and a zincate.

[0037] The production method described above makes it possible to obtain coated steel parts suitable as first and / or second landing gear parts for producing static sealing points as described above. In particular, it makes it possible to obtain zinc and nickel alloy coatings having average surface roughnesses Ra less than or equal to 1.6 µm.

[0038] In one embodiment, the substrate preparation step may include a sandblasting step.

[0039] In another embodiment, the substrate preparation step may comprise a chemical etching step.

[0040] For example, chemical etching can be carried out using a 3% aqueous hydrochloric acid solution.

[0041] A preparation step comprising chemical etching is particularly preferred because it makes it possible to obtain, immediately after the chemical etching, a very low roughness, which will facilitate obtaining low roughness after the electrolytic deposition step.

[0042] In one embodiment, the method may further comprise, after the electroplating step, one or more finishing steps.

[0043] For example, in one embodiment, the finishing step is a mechanical polishing step.

[0044] This step further reduces the surface roughness obtained for the zinc and nickel alloy coating at the end of the preparation process.

[0045] In this embodiment, the method may further comprise a passivation step after the mechanical polishing step.

[0046] Such a passivation step makes it possible to improve the corrosion resistance properties of the alloy, without in any way harming the low roughness obtained after mechanical recovery.

[0047] In one embodiment, the method further comprises, after the electrolytic deposition step, a step of applying an organo-mineral composition to the zinc and nickel alloy coating.

[0048] For example, such an organo-mineral composition may comprise a mixture of silicic acid, lithium salt, ethoxylated alcohol with 16 to 18 carbon atoms and ammonia.

[0049] The application of an organo-mineral composition makes it possible to further reduce the surface roughness, especially when the surface roughness is not as low as desired after the electrolytic deposition step. Brief description of the drawings

[0050] [ Fig. 1 ] There Figure 1 schematically represents a lander in one embodiment of the invention. Description of the embodiments

[0051] The invention is now described by means of particular embodiments and examples, which are described for illustrative purposes, and should not be construed as limiting the invention.

[0052] As described above, the invention relates to a landing gear comprising: a landing gear rod extending along a main axis; at least one axle mechanically connected to the landing gear rod; at least one wheel mounted to be able to be rotated around said axle; at least one shock absorber arranged to dampen a sliding movement of said rod relative to a structure of the aircraft, the landing gear being characterized in that it further comprises at least one static sealing point as described above.

[0053] Conventionally, the landing gear may comprise a plurality of static sealing points, ensuring proper operation of the shock absorber.

[0054] As indicated above, the static sealing points comprise a seal made of elastically deformable material held between a portion of a first part of the landing gear and a portion of a second part of the landing gear, the first and second parts comprising a steel substrate coated with a zinc and nickel alloy coating, comprising, as a mass percentage of the alloy, between 12% and 18% and nickel, at most 0.5% of elements other than nickel and zinc, the remainder being zinc, and the roughness Ra of the surface of the portions of the first and second parts of the landing gear being less than or equal to 1.6 µm.

[0055] In one embodiment, the zinc-nickel alloy coating may cover a larger portion of the first and / or second landing gear part than just the static sealing point.

[0056] For example, the alloy coating may cover the entire first and / or second part of the lander, in order to also take advantage of the improved corrosion resistance properties provided by the zinc and nickel alloy coating as described above.

[0057] Thus, the preparation of a landing gear is simplified compared to the preparation of a landing gear of the prior art, because it is no longer necessary to distinguish the coatings to be applied to obtain a static sealing point and to obtain a part having good corrosion resistance.

[0058] Reference is made to the Figure 1 which describes a lander in one embodiment of the invention seen in section.

[0059] In this embodiment, the landing gear 100 comprises a wheel 11 mounted on an axle 12.

[0060] The axle 12 is carried inside a U-shaped rod 21, each of the arms of the rod 21 extending into a chamber 32 formed by the outer wall 31 of the landing gear. The two arms of the rod 21 extend into the chamber 32 and parallel to the outer wall 31. The arms of the rod 21 are further secured to a lug 22 which extends parallel to the arms of the rod 21 in the center of the chamber 32.

[0061] The two branches of the rod 21 and the leg 22 are free to move in only one direction, the vertical direction in the mode shown.

[0062] Thus, a movement of the axle 12 causes a displacement of the two branches of the rod 21 and the lug 22 relative to the outer wall 31.

[0063] According to the principle of a conventional shock absorber, the chamber 32 of the landing gear 100 can be filled with a liquid, the viscosity of which is chosen to dampen the movements of the arms of the rod 21 or the leg 22 so that the axle and the wheel that it carries see their movements dampened.

[0064] In the embodiment shown, the tab 22 engages in an internal portion of the chamber 32 delimited by an internal wall 33. The internal portion delimited by the internal wall 33 is however in fluid communication with the rest of the chamber 32.

[0065] The landing gear further comprises one or more static sealing point(s) 40, also identified by circles in the figure.

[0066] These sealing zones ensure that the contents of chamber 32 do not come into contact with the outside.

[0067] As described above, a method is also provided for obtaining a part comprising a steel substrate coated with a zinc and nickel alloy coating comprising, as a mass percentage of the alloy, between 12% and 18% and nickel, at most 0.5% of elements other than nickel and zinc, the remainder being zinc, the surface of which has a roughness Ra less than or equal to 1.6 µm. In particular, this method makes it possible to obtain first and / or second parts for static sealing zones as described above.

[0068] The method comprises a first step of degreasing the substrate. This step is present in order to remove any contaminants from the surface. In particular, such a step can remove traces of oil, grease and / or foreign matter that could result from the preparation of the substrate. For example, the degreasing step can be carried out with a formulation comprising sodium metalisilicate, diphosphoric acid, ethoxylated alkyl alcohol, and amines. Such a formulation is, for example, commercially available under the name Turco C-AK Aviation.

[0069] The process also includes a second step of etching the substrate. This step aims to activate the surface of the substrate, and thus increase its reactivity in order to promote the deposition of the zinc and nickel alloy coating.

[0070] In one embodiment, this step may be a mechanical step. For example, the substrate stripping step may be a mechanical sandblasting step.

[0071] In another embodiment, the stripping step may be a chemical step. For example, the stripping step may be carried out by soaking a piece of substrate obtained after the degreasing step in a 175 g / L hydrochloric acid solution comprising 5% of an additive, for example available under the trade name Picklane 50. The soaking may take place for 5 minutes at 20°C.

[0072] The third step of the process is the step of forming the zinc and nickel alloy coating on the surface of the pickled substrate, obtained at the end of the second step, by dipping it into an electrolytic bath.

[0073] The substrate piece can be immersed in an alkaline bath containing nickel sulfate and zincate.

[0074] An electrical potential is applied between the substrate piece and an electrode immersed in the electrolytic bath.

[0075] For example, the alkaline bath can be obtained by pouring into the bath a solution of sodium hydroxide and / or potassium hydroxide, nickel in the form of nickel sulfate, zinc in the form of zincate and complexing agents necessary for the complexation of zinc and nickel such as amines such as diethylene triamine and organic additives such as brighteners or leveling agents.

[0076] If necessary, depending on the geometry of the first part, other anodes can be used to create add-on tools facing areas of the first part that are difficult to access. To limit local excess thickness, it is also possible to place covers and / or current stealers facing portions of the first part. This tooling, consisting of anodes, covers and current stealers, allows for a uniform thickness during deposition.

[0077] The time taken to complete the deposition and the current density imposed between the anodes and the first part immersed in the bath define the final thickness of the zinc-nickel layer obtained. These tools and time and current density parameters are adjusted to obtain a predetermined final layer thickness.

[0078] An optional passivation step can be carried out after the electrolysis treatment. This step increases the corrosion resistance provided by the zinc and nickel coating.

[0079] Such a step can be carried out by immersion in a room temperature bath. For example, the immersion can be carried out for 60 seconds.

[0080] As mentioned above, the proposed zinc and nickel alloy coating also provides the substrate with good corrosion resistance properties. When such corrosion resistance properties are required, and since this does not adversely affect the surface roughness, it is advantageous to carry out a passivation treatment on the entire first and / or second part. This will allow, with a single coating, to provide both the desired corrosion resistance and static sealing properties. The coating is also more environmentally friendly than the chromium and / or nickel coatings currently available for these two applications. Finally, obtaining a single coating with both properties facilitates the preparation of the landing gear parts.

[0081] In one embodiment, the method may further comprise a step of degassing the hydrogen occluded in the steel. For example, such a step may be carried out by heating the coated part for at least 12 hours in a furnace at a temperature between 176°C and 204°C. Such a step makes it possible to evacuate any hydrogen formed during electrolysis. Indeed, the part is generally placed at the cathode during this step, and it is possible that gaseous hydrogen is released at the cathode and diffuses into the material. This step therefore allows the evacuation of this hydrogen, and thus reduces the fragility of the final part.

[0082] As described above, it is possible after this process treatment to further reduce the average roughness of the surface coating by means of a mechanical reworking step or by applying an organo-mineral layer.

[0083] In a first embodiment, the method further comprises a finishing step by mechanical reworking. This step can be carried out by means of polishing using an abrasive belt.

[0084] In another embodiment, the method further comprises a finishing step by applying an organo-mineral resin.

[0085] Such a step allows, by coating the surface with an organo-mineral resin, to reduce the roughness of the surface of the part obtained at the end of the electrolytic treatment. Indeed, the organo-mineral resin will be deposited in the asperities of the surface and finally form a thin film whose surface will be less rough than the surface of the coated substrate part.

[0086] The inventors found that a finishing step is particularly advantageous when the substrate preparation step was carried out by sandblasting. It is indeed found that the average roughness of the coated substrates obtained at the end of the electrolysis step is lower when the preparation step is chemical stripping than mechanical polishing.

[0087] However, it is possible to avoid this step, because the coating obtained at the end of the electrolysis step generally has satisfactory roughness.

[0088] Whatever the treatment chosen, and whether or not there is a finishing step.

[0089] The invention is now described by means of exemplary embodiments. Examples Example 1: leak test on witness pieces.

[0090] In this example, the sealing of witness pins representative of the static sealing points is tested. The witness pins comprise an elastomeric seal made of ethylene-propylene, the seal being an O-shaped ring, held between a first part made of 35NCD16 steel covered with a zinc and nickel alloy coating comprising 12 to 18% nickel and the remainder zinc, and a second part made of a metal substrate coated with a zinc and nickel alloy comprising 12 to 18% nickel and the remainder zinc.

[0091] The surfaces of the parts are prepared by means of an electrolytic process similar to that of the invention described above but by adjusting the production parameters so that certain parts are obtained with average roughnesses in accordance with the invention and others with higher roughnesses.

[0092] The parts may or may not include finishing steps to reduce the roughness of their surfaces, in particular a step of depositing an organometallic resin, or a mechanical reworking step.

[0093] The protocols for the leak tests carried out are as follows: for the nitrogen leak test at 150 bars: the valve representing the sealing zone is screwed into the sample with a torque between 12 and 12.5 Nm. Then the sample is inflated by a nitrogen flow to a pressure of 150 bars. A second valve called the pressure closure valve is closed with a torque of 12 to 12.5 Nm to keep the sealing zone to be tested under pressure.

[0094] To detect a leak, a foaming fluid is applied to the pin every day for 7 days. If foam appears, the part is declared non-tight (noted NOK in the tables below). On the other hand, if no foam is observed even after 7 days, the part is declared tight (noted OK in the tables below). for the hydraulic fluid leak test at 150 bar: 1 mL of phosphorescent fluid is introduced into the reservoir of the sealing pin. The rest of the reservoir is filled with FH51 hydraulic fluid. The valve representing the sealing area to be tested is screwed into the sample with a torque between 12 and 12.5 Nm. The sample is inflated using FH51 hydraulic fluid to a pressure of 150 bar. A second valve, called a pressure shut-off valve, is closed with a torque of 12 to 12.5 Nm to pressurize the sealing area to be tested. The resulting part is inspected every day for 21 days under ultraviolet radiation to see whether or not the phosphorescent fluid has escaped from the sealing pin. If the phosphorescent fluid appears, the part is declared non-watertight (noted NOK in the tables below) while if the phosphorescent fluid does not appear, the part is declared watertight (noted OK in the tables below).

[0095] The test results for this example are shown in Table 1 below.

[0096] In the example tables, OK indicates that the leak test was successful, while NOK indicates the opposite. -- indicates that the measurement was not performed. The zinc nickel finish column indicates whether or not a treatment was performed after the electrolytic deposition stage of the coating. [Table 1] Zinc nickel finish Average Ra (µm) 150 bar nitrogen leak test Hydraulic fluid leak test 150 bars None 2,2 OK OK None 3,6 NOK NOK Organometallic finish 1,5 OK OK Mechanical recovery 0,2 OK OK

[0097] Table 1 shows that for control pieces, the sealing is not a function of the presence or absence of a finishing step on the coating, but that on the other hand, when the roughness becomes too significant, the sealing is no longer ensured. Example 2: leak tests on an axis

[0098] In this example, a cylindrical steel part is coated with a zinc and nickel alloy coating. Around this cylindrical part, serving as the first surface, are placed two elastomeric seals.

[0099] The elastomeric seals are then covered by a second steel part whose surface is coated with a zinc and nickel alloy coating, thus forming two static sealing zones.

[0100] The surfaces of the parts are prepared by means of an electrolytic process similar to that of the invention described above but by adjusting the production parameters so that certain parts are obtained with average roughnesses in accordance with the invention and others with higher roughnesses.

[0101] The static sealing areas are then tested by applying a flow of nitrogen at 100 bar between the two sealing areas and immersion in an oil bath to visually determine whether or not the nitrogen is able to pass through the static sealing area.

[0102] The sealing areas are considered compliant if after 6 minutes, no bubbles, or only a few small diameter bubbles are observed (noted OK in the table below).

[0103] If a few bubble paths of a large diameter, or many large bubble paths are observed, the sealing areas are considered unsatisfactory (noted NOK in the table below).

[0104] The test is carried out for several surfaces prepared by a process similar to that of the invention, possibly including a finishing step by mechanical polishing. [Table 2] Zinc Nickel Finish Average Ra (µm) 100 bar nitrogen leak test None 3,3 OK 4,7 NOK 4,5 NOK Mechanical recovery 3,3 OK 3,5 OK 2,6 OK

[0105] Table 2 illustrates in the case of cylindrical model parts that the sealing is not linked to the presence or absence of a finishing step, and also demonstrates that when the roughness exceeds a limit value, the sealing is no longer ensured.

[0106] Example 3: Leak tests on real parts.

[0107] Static sealing areas for actual landing gear parts are made by a method as described above.

[0108] The surfaces of the parts are prepared by means of an electrolytic process similar to that of the invention described above but by adjusting the production parameters so that certain parts are obtained with average roughnesses in accordance with the invention and others with higher roughnesses.

[0109] The seal is tested between two static sealing zones, as in example 2.

[0110] The gas tightness of static sealing zones is tested by subjecting the space between two static sealing zones to a nitrogen pressure of 100 bars for 10 to 12 minutes in an oil bath. If at most two lines of bubbles are detected, the part is considered leaktight (noted OK in the table below), and non-leaktight if more bubbles are detected.

[0111] Static fluid tightness is also tested using a similar method to that described in example two, but at a pressure of 172 bar for 2 minutes and then 97 bar for 12 hours. If no leaks are detected, the part is deemed leaktight (noted OK in the table below), and not leaktight otherwise.

[0112] The results are presented in the table below for different samples. [Table 3] Zinc Nickel Finish Average Ra (µm) Nitrogen leak test 100 bars 10 min Hydraulic leak test 172 bars 2 min + 97 bars 12 h None 0,9 OK OK None 1,1 OK OK None 1,7 NOK -- Mechanical recovery 0,8 OK OK Mechanical recovery 1,0 OK OK Mechanical recovery 0,8 OK OK

[0113] Table 3 illustrates a behavior similar to that of the control parts of Examples 1 and 2, namely that the sealing or not of a part is not a function of a finishing treatment or not. It is also observed that when the average surface roughness exceeds 1.6 µm, sealing is no longer ensured, while as long as the surface roughness remains below 1.6 µm, the static sealing zones are satisfactory. Example 4

[0114] Static sealing areas are prepared on cylindrical landing rods coated with nickel and zinc coating.

[0115] The surfaces of the parts are prepared by means of an electrolytic process similar to that of the invention described above but by adjusting the production parameters so that certain parts are obtained with average roughnesses in accordance with the invention and others with higher roughnesses. The sealing is tested between two static sealing zones, as in example 2.

[0116] Static fluid tightness is tested using a similar method to that described in Example 2, but with a pressure of 5, 12 or 150 bars. If no leak is detected, the part is deemed leaktight (noted OK in the table below), and otherwise non-leaktight (noted NOK). [Table 4] Zinc nickel finish Average Ra (µm) 5 bar hydraulic leak test 12 bar hydraulic leak test Hydraulic leak test 150 bars None 0,3 OK OK OK None 0,5 OK OK OK None 2,0 OK OK OK

[0117] The examples described in Table 4 show that the hydraulic sealing is satisfactory for real landing gear parts even when the average roughness is slightly higher.

[0118] The above examples clearly demonstrate that the parts conforming to the subject of the invention have static sealing characteristics superior to parts outside the invention.

Claims

1. A landing gear (100) comprising: - a landing gear rod (21) extending along a main axis; - at least one axle (12) mechanically connected to the landing gear rod; - at least one wheel (11) mounted to be able to be rotated around said axle; - at least one damper disposed to damp a sliding movement of said rod relative to a structure of the aircraft, the landing gear further comprising at least one static sealing point (40), the static sealing point comprising a gasket made of elastically deformable material held between a portion of a first part of the landing gear and a portion of a second part of the landing gear, the first and second parts of the landing gear comprising a steel substrate coated with a coating, the landing gear being characterized in that the coating at the static sealing point is a zinc and nickel alloy coating including in mass percentage of the alloy between 12% and 18% and nickel, at most 0.5% of elements other than nickel and zinc, the balance being zinc, and the roughness Ra of the surface of the portions of the first and second parts of the landing gear is less than or equal to 1.6 µm.

2. The landing gear (100) according to claim 1, wherein the zinc and nickel alloy coating has a thickness comprised between 10 and 30 µm.

3. The landing gear (100) according to any one of claims 1 or 2, wherein the gasket made of elastically deformable material is composed of one or more materials selected from: polybutadiene, chlorinated polyethylene, chloroprene, polyethylene chlorosuflon, fluorocarbons, fluorosilicones, hydrogenated nitriles, polyacrylates, perfluoroelastomers, polyacrylates, polyurethanes, silicone and its derivatives, or else from nitrile-butadiene, ethylene-propylene, ethylene-acrylate, isobutylene copolymers and isoprene, styrene-butadiene, tetrafluoroethylene and propylene.

4. The landing gear (100) according to any one of claims 1 to 3, wherein at least one of the surfaces of the first and second parts comprises an organo-mineral layer on the zinc and nickel alloy coating and in contact with the latter.

5. The landing gear (100) according to any one of claims 1 to 4, wherein the steel substrate of the first and second parts is selected from the following steels: 35NCD16, 35CD4, 35NC6, S99, S154, 25CD4S, Z8CND17-04, Z6CNU17-04, Z15CN17-03, S143, S144, S145, Z2CN18-10, Z2CN18-10 / Z3CN18-10, Z10CNT18-10, Z12CNT18-10, XES, XC18S, 17-4PH, X2CrNi 18-9, 304L, Z6CNT18, 17-7PH, DC04 or C22E / R.