Method for coating a wheel hub assembly

Abstract

A method for coating exposed surfaces of a wheel hub assembly comprising a respective first flange and a second flange rigidly attached in a radially outer side to an outer ring and an inner ring of rolling bearings rotatable relative to each other, the wheel hub assembly being mounted in a protruding manner on a rotatable first main shaft until the wheel hub assembly comes into contact against an annular shield configured in a radially outer side of the first main shaft; a layer of a zinc flake coating material is sprayed using an air spray nozzle onto a first exposed surface of the wheel hub assembly while the main shaft is rotating, said layer being subsequently solidified by means of IR irradiation while the wheel hub assembly is rotating; during both steps, a second exposed surface of the wheel hub assembly is shielded by the annular shield, by a masking tape configured between the first flange and the second flange in the spraying step and by a thermal shield.

Description

Technical Field

[0001] This invention relates to a method for coating exposed surfaces of a wheel hub assembly for vehicles. The invention also relates to an associated wheel hub assembly having a corrosion-resistant protective layer applied to specific exposed surfaces. Background Technology

[0002] Suspensions for vehicles (particularly motor vehicles) are known to include wheel hub assemblies for rotatably supporting the vehicle wheels. The wheel hub assembly comprises or is formed of rolling bearings, in which inner and outer rings are attached to corresponding mounting flanges; that is, a first flange configured to receive the vehicle wheel and a second flange capable of securing the wheel hub assembly to the vehicle suspension strut.

[0003] In modern wheel hub assemblies, the inner and outer rings of the rolling bearings are directly provided with the aforementioned first and second flanges as a single piece. Typically, the first flange for wheel support is integrally formed with the inner ring or a component of the inner ring's main shaft, and the second flange for mounting on the vehicle suspension is integrally formed with the outer ring on its radially outer side.

[0004] In particular, the second flange and the exposed portion of the rolling bearing near the second flange may be subject to corrosion during use.

[0005] WO2019015712 discloses a method for completely coating a wheel hub assembly with a zinc flake coating, wherein all exposed surfaces of the components of the wheel hub assembly (i.e., those exposed surfaces facing radially outward, such as the inner and outer rings and at least a portion of the radially outer surfaces of the corresponding flanges) are covered with the zinc flake coating by spraying or immersion in a suitable bath and subsequently hardening (curing) by treatment in a convection oven. According to WO2019015712, curing is carried out at a curing temperature of at least 15°C and at most 80°C, for a curing time of at least 10 minutes, but typically close to 16 minutes. Any uncoated portions of the wheel hub assembly must be masked, for example, covered with protective tape.

[0006] More generally, zinc flake coatings are well known in the art, particularly for coating large structures and fasteners. Specifically, specifications for zinc flake coatings are defined in international standard ISO 10683 and European standard EN 13858. ISO 10683 specifies the requirements for zinc flake coatings used in threaded fasteners, while EN 13858 describes the requirements for zinc flake coatings used in unthreaded fasteners.

[0007] In summary, according to the method of WO2019015712, at least 10 minutes are required for each wheel hub assembly to ensure that the applied coating is completely dry and hardened and to provide a coating thickness between 10 and 20 micrometers. Larger thicknesses are prone to cracking.

[0008] Furthermore, the use of convection ovens (such as tunnel ovens) requires significant energy and large-scale facilities, resulting in high costs. Then, the heat energy provided to reach the necessary temperatures in the zinc coating is also transferred within the wheel hub assembly, potentially creating criticalities for the lubricant applied between the rings of the rolling bearings to lubricate the rolling elements and for the sealing gaskets. Summary of the Invention

[0009] The present invention aims to provide a method for coating exposed surfaces of wheel hub assemblies that does not have the aforementioned disadvantages, particularly in that it can obtain zinc flake coatings on heat-damage-sensitive components such as wheel hub assemblies, with reduced energy consumption, smaller mounting dimensions, good coating thickness, and shortened curing time, all using commercially available zinc flake coating products (i.e., those used for fasteners and other applications).

[0010] The present invention also aims to provide an associated wheel hub assembly provided with a zinc sheet coating obtained according to the method described above, which can be implemented in an associated facility.

[0011] According to the present invention, a method for coating an exposed surface of a wheel hub assembly having the features set forth in the appended claims is provided, as well as an associated wheel hub assembly.

[0012] In this context and below, "exposed surface" is understood to mean the portion facing the outside of the wheel hub assembly, such as the radially lateral surfaces of the inner and outer races of the rolling bearings of the wheel hub assembly, and the outer surface of the corresponding mounting flange of the wheel hub assembly. Attached Figure Description

[0013] The invention will now be described with reference to the accompanying drawings, which illustrate non-limiting exemplary embodiments of the invention, in which:

[0014] - Figure 1 The diagram schematically illustrates a first step of the method according to the invention, which is applied, by means of facilities associated with the method of the invention (shown only partially for simplicity), to a wheel hub assembly of a known type; and

[0015] - Figure 2The second step of the method according to the invention and the resulting wheel hub assembly are schematically illustrated. The second step of the method of the invention is achieved by means of... Figure 1 The method of the present invention is implemented by means of facilities associated with it, which are only through its connection with Figure 1 Different parts or through with Figure 1 They are shown as identical parts but in different structures. Detailed Implementation

[0016] Figure 1 and Figure 2 The diagram schematically illustrates two steps of a method for coating the exposed surface 2 of a wheel hub assembly 1, which includes or is formed of a rolling bearing 3, which in turn includes an outer ring 4 and an inner ring 5, which are rotatable relative to each other by means of a known rolling element between them, which is not shown for simplicity.

[0017] The wheel hub assembly 1 also includes corresponding first mounting flange 6 and second mounting flange 7 rigidly attached to the outer ring 4 and the inner ring 5 on the radially outer side, respectively. The first flange 6 is rigidly attached to the outer ring 4 and the second flange 7 is rigidly attached to the inner ring 5.

[0018] In the non-limiting example shown, the rolling bearing 3 constitutes the entire wheel hub assembly 1, and the flanges 6 and 7 are integrally formed with the rings 4 and 5 on the radially outer side of the rings 4 and 5.

[0019] In other possible embodiments, which are not shown for simplicity, flanges 6 and 7 are indirectly attached to rings 4 and 5 by means of other components known in the wheel hub assembly 1 itself. For example, the inner ring 5 may be mounted on a spindle with flanges 7 at its ends.

[0020] The flange 6 is adjacent to the first end 8 of the wheel hub assembly 1. In the example shown, the first end 8 is formed by a corresponding sleeve-shaped end 9 of the outer ring 4 that protrudes axially from the flange 6.

[0021] In the preferred embodiment shown, the first exposed surface 2 includes at least the front surface 10 of the first flange 6 and the radially outer peripheral edge 11.

[0022] The wheel hub assembly 1 also includes a second exposed surface generally indicated by 12, which is generally formed by the outer surface of the flange 7 and the lateral surfaces of the rings 4 and 5. In this case, it does not include the radially outer lateral surface of the sleeve-shaped end 9 of the outer ring 4, which forms part of the first exposed surface 2. According to the method of the invention, the first exposed surface 2 must be protected, for example by increasing its corrosion resistance.

[0023] First, the exposed surfaces 2 to be protected, or even all external exposed surfaces 2 and 12, of the wheel hub assembly 1 must be treated with a cleaning agent (known and not shown for simplicity) to remove any trace amounts of oil, grease or other contaminants present on the exposed surfaces 2 and 12 due to various machining and installation steps.

[0024] The cleaning agent is preferably a solvent containing a detergent fluid. Solvents containing detergent fluid are characterized by rapid action, good material compatibility, and ease of application. Therefore, the cleaning agent does not react with the material of the surface 2 to be treated or the wheel hub assembly 1. Preferably, the cleaning agent is sprayed onto the surface of the component to be treated; it is also conceivable that the cleaning agent is applied manually to the wheel hub assembly 1.

[0025] After the cleaning agent has been applied to the surface 2 of the component to be treated, the wheel hub assembly 1 is rotated at high speed so that the excess cleaning agent is removed by the centrifugal force generated on the surface 2 of the component.

[0026] Following this preliminary step and referring to Figure 1 According to the method of the invention, the step of mounting the fully assembled wheel hub assembly 1 (thus completed with internal lubricant and sealing gaskets) in a protruding manner onto the first motorized spindle 13 is performed, by assembling the wheel hub assembly 1 onto the first spindle 13 via the first flange 6 until the first end 8 of the wheel hub assembly 1 adjacent to the first flange 6 abuts against the annular screen 14, which in the illustrated example has a cup-shaped concave shape and a truncated conical profile and is mounted radially outward of the first spindle 13.

[0027] In this step, the wheel hub assembly 1 is angularly and rigidly mounted to the main shaft 13 so that it can rotate together with the main shaft 13. The screen 14 can also be angularly and rigidly mounted to the main shaft 13, or mounted radially outward of the main shaft 13, but in a fixed (stationary) manner, and therefore the screen 14 remains stationary when the motorized and controlled main shaft 13 rotates together with the wheel hub assembly 1 as a whole. In both cases, as... Figure 1 As schematically indicated by the circle, the annular shield 14 is separated from the sleeve-shaped end 9 of the outer ring 4 only by a very small axial gap 15, thereby effectively forming a labyrinth seal between the shield 14 and the end 8 of the wheel hub assembly 1.

[0028] When the wheel hub assembly 1 rotates about the main shaft 13 and the common axis of symmetry A of the wheel hub assembly 1, according to one aspect of the invention, the step of applying layer 16 of zinc sheet coating material 18 is performed by activating the main shaft 13 by rotating it at a predetermined first speed.

[0029] Floor 16 Figure 1 The image is schematically shown in thick lines, and layer 16 is deposited on all the first exposed surfaces 2 of the wheel hub assembly 1, which, as already indicated, include at least the front surface 10 of the first flange 6 and the radial outer peripheral edge 11.

[0030] According to one aspect of the invention, the step of applying zinc sheet coating material 18 (which is known and commercially available for other purposes) to form layer 16 is performed by means of air spray nozzle 19, while the wheel hub assembly 1 rotates about axis A by means of main shaft 13, and as the wheel hub assembly 1 rotates, all of the nozzles 19 together or sequentially are positioned in front of the first exposed surface 2 at a predetermined distance from said surface.

[0031] The layer 16 of zinc sheet coating material 18 deposited on the first exposed surface 2 of the wheel hub assembly 1 is deposited not only on the front surface 10 and radial outer peripheral edge 11 of the first flange 6, but also at least on the radial outer surface 17 of the outer ring 4, which defines the first end 8 of the wheel hub assembly 1 and thus forms an integral part of the first exposed surface 2.

[0032] According to one aspect of the invention, as will be seen, the second exposed surface 12 of the wheel hub assembly 1, which does not need to be coated with material 18, is shielded by means of an annular shield 14 and by means of at least one shielding strip 20 to prevent possible over-coating.

[0033] In fact, the main disadvantage of spraying material 18 mixed with pressurized air in or immediately upstream of the spray nozzle 19 in a known manner is that it may produce a spray “mist” around the exposed surface 2. While this allows material 18 to be deposited uniformly to produce layer 16, on the other hand, the sprayed material 18 that is not deposited on surface 2 remains suspended in the ambient air and may be partially deposited randomly on surface 12 in an undesirable manner.

[0034] According to one aspect of the invention, at least one shielding strip 20 is stretched and disposed in the axial space between the first flange 6 and the second flange 7 to protect the second exposed surface 12 located on the second flange 7 and at the second end 21 of the wheel hub assembly 1 opposite to the first end 8.

[0035] Preferably, the shielding tape 20 is unwound from and wound onto a pair (e.g., motorized) rotatable spools 22. Figure 1 Only one of the scrolls is shown in the diagram, because scroll 22 is positioned on opposite sides (flanks) of the first main shaft 13 in diameter, and therefore the second scroll 22 is not visible because it is hidden by the first scroll.

[0036] although Figure 1 A single shielding strip 20 supported by a reel 22 is shown, but it is clear that more shielding strips 20 (not shown for simplicity) can be provided as needed. The shielding strips 20 are oriented in different ways and are configured to intercept all material 18 that is oversprayed by the nozzle 19 and remains suspended in the atmosphere.

[0037] exist Figure 1 In the non-limiting example embodiment shown, the motorized spindle 13, reel 22, belt 20 and nozzle 19 form part of a first processing station 23, which also includes hydraulic circuits 24 connected upstream and downstream of the nozzle 19.

[0038] The hydraulic circuit 24 includes a tank 25, a supply line 25 for the nozzle 19, and a recirculation line 27. The tank 25 is equipped with a suitable circulation pump (not shown for simplicity), and the material 18 stored in the tank 25, which has not yet been mixed with the compressed air in the nozzle 19 and is being transported back to the tank 25, flows in the recirculation line 27.

[0039] In fact, according to one aspect of the invention, the zinc sheet coating material 18 is continuously recirculated within the hydraulic circuit 24 connected to the nozzle 19.

[0040] During the step of depositing / applying material 18 onto surface 2 to form layer 16, the first spindle 13 rotates between approximately 120 rpm and approximately 150 rpm, and the zinc sheet coating material 18 is discharged from nozzle 19 at an overpressure between approximately 0.45 bar and approximately 0.9 bar relative to atmospheric pressure, and preferably at a temperature between 10°C and 40°C.

[0041] When nozzle 19 is not in operation, material 18 remains in circulation within hydraulic circuit 24, preferably at a pressure greater than the pressure at which material 18 is distributed from nozzle 19.

[0042] Although for the sake of simplification, axis A is... Figure 1 Positioned horizontally, but it is clear that the axis of rotation A of the main shaft 13 can also be horizontal or vertical. Each solution has its advantages and disadvantages, depending primarily on the density and viscosity of the zinc flake coating material 18, which can be added to the storage tank 25 along with a type of diluent suitable for altering its rheological properties in a desired manner.

[0043] Now refer to Figure 2 Details similar to or identical to those already described are indicated by the same reference numerals. A second processing station 23b is shown, which is configured to perform a subsequent step of the method of the invention, specifically, to cure and related harden the layer 16 of material 18 that has just been deposited on the exposed surface 2.

[0044] In fact, during the preceding steps of depositing layer 16, material 18 can be mixed with volatile solvents. In particular, the components of zinc sheet coating material 18 may include (as known) temperature-sensitive organic or inorganic polymerizable matrices. In a sense, the higher the temperature of material 18 after forming layer 16, the faster material 18 hardens and dries.

[0045] According to one aspect of the invention, and in conjunction with the foregoing, the step of curing the zinc sheet coating material 18 deposited on surface 2 to form its coating 16 comprises: on a second motorized spindle 13b that has been angularly and rigidly mounted on the same spindle 13 or substantially the same as the first spindle 13 (or the same as the first spindle 13). Figure 2After being coaxial with the main shaft 13 or the second motorized main shaft 13b, the wheel hub assembly 1 is rotated about its axis of symmetry A, and then heated by irradiating the exposed surface 2 by means of the IR lamp 28 while the wheel hub assembly 1 is rotating at a predetermined speed by means of the main shaft 13 or 13b.

[0046] It should be noted that, for the sake of simplicity, station 23 and station 23b are shown as two separate stations, forming part of the same facility configured to perform the method of the present invention. In practice, a single station 23 may exist, comprising a single spindle 13 and may be configured to selectively employ… Figure 1 and Figure 2 Two structures in it.

[0047] Therefore, in this step, the wheel hub assembly 1 is also angularly and rigidly mounted on the same first spindle 13 via the first flange 6 (and in the already performed Figure 1 After the steps in the middle, it is held angularly and rigidly mounted on the main shaft 13 or the same second main shaft 13c until the first end 8 of the wheel hub assembly 1 adjacent to the first flange 6 abuts against the same annular screen 14 or another identical annular screen 14, which is mounted radially outside the first annular main shaft 13 or the second annular main shaft 13b and thus with Figure 1 The same as shown.

[0048] Therefore, the first exposed surface 2 is heated by irradiation with IR lamps 28, while the wheel hub assembly 1 is rotating, all of the IR lamps 28 are placed together or in sequence in front of the first exposed surface 2 at a predetermined distance from the first exposed surface 2 until the layer 16 of the previously applied zinc sheet coating material 18 is completely cured.

[0049] exist Figure 2 In station 23b, the axis of rotation A is shown in a vertical position for simplification, but as in Figure 1 In the case shown in the steps, the axis of rotation A can also be oriented horizontally or vertically.

[0050] During this curing step by heating, the annular shield 14 is also separated from the sleeve end 9 only by a very small axial gap 15, thereby effectively forming a labyrinth seal between the shield 14 and the end 8 of the wheel hub assembly 1.

[0051] In the steps of depositing zinc flake coating 16 and curing zinc flake coating by localized heating, the nozzle 19 and IR lamp 28 are positioned together or sequentially one at a time in front of the first exposed surface 2 by moving the nozzle 19 and IR lamp 28 relative to the first spindle 13 or the second spindle 13b (e.g. by means of one or more robotic arms), or similarly by moving the spindle 13 and / or 13b toward the nozzle 19 and / or IR lamp 28.

[0052] For example, in one embodiment, the facility for performing the method of the present invention includes a single station 13 or multiple stations 13 operating in parallel, which are served by robotic arms carrying nozzles 19 and lamps 28. In different embodiments, multiple identical spindles 13 are mounted on a rotary table that conveys each spindle 13 through multiple stations, such as stations for mounting / removing wheel hub assemblies 1 onto / from spindles 13, stations for depositing layers 16 with at least one nozzle 19 in a fixed or movable position by means of a robotic system, and one or more curing stations, all equipped with IR lamps 28, with the spindle 13 passing along the curing stations to complete the process of heating and hardening the layer 16 on each wheel hub assembly 1.

[0053] In any case, the curing step is performed for a duration not exceeding 480 seconds, preferably for a duration of 360 seconds, and each station 23 / 23b uses at least one pair of IR lamps with a power of approximately 3000 watts and configured to be opposite the first exposed surface 2.

[0054] In any case, whether in the same station or through multiple stations 23 / 23b, the curing step is performed by rotating the wheel hub assembly 1 about its axis of symmetry A at a speed of approximately 60 rpm (that is, slower than the speed used in the step of applying layer 16) by means of the first spindle 13 or the second spindle 13b.

[0055] According to one aspect of the invention, during the curing step by only locally heating the exposed surface 2, the entire wheel hub assembly 1, except for the first exposed surface 2, is shielded from the short- or medium-wavelength IR (infrared) radiation beams 29 emitted by the IR lamp 28 by means of an annular shield 14 (therefore having a dual function (preventing over-spraying and preventing radiation 29)) and by means of a heat shield 30 disposed between the IR lamp 28 and the second exposed surface 12 of the wheel hub assembly 1.

[0056] The heat shields 30 are preferably attached laterally and rigidly to the IR lamp 28 so that they can move with the IR lamp.

[0057] Comparative experimental tests conducted by the applicant have demonstrated that the method of the present invention enables the zinc flake coating 16 previously deposited on surface 2 to reach a temperature of 120°C within a very short time period of no more than 480 seconds (approximately 8 minutes) and an average of 360 seconds (6 minutes), achieving complete curing of layer 16 and ensuring that the internal temperature of the wheel hub assembly 1 does not exceed 60°C to 80°C, typically less than 60°C. Conversely, even when the cured layer 16 has a thickness greater than 20 micrometers, or even up to approximately 35 micrometers, optimal results can be obtained in terms of the resistance and sealing of the cured layer 16, resulting in optimal protection of the treated exposed surface 2.

[0058] Finally, it is clear from the foregoing that the present invention also relates to a wheel hub assembly 1 for a motor vehicle, the wheel hub assembly 1 including a rolling bearing 3, the rolling bearing 3 further including an outer ring 4 and an inner ring 5 rotatable relative to each other, and corresponding first mounting flanges 6 and second mounting flanges 7 respectively directly or indirectly rigidly attached to the outer ring 4 and the inner ring 5 radially outward, wherein a first exposed surface 2 of the wheel hub assembly 1 (including at least the front surface 10 of the first flange 6 and the radially outer peripheral edge 11 (preferably also including surface 17)) is coated with a layer 16 of zinc flake coating material, the layer 16 of which has been made by means of the described coating method and has a radial thickness between 9 micrometers and 35 micrometers, and is free from cracks.

[0059] With the method described, it is clear that a shorter cycle time than the prior art can be obtained, and a high-value film layer with a thickness of up to 35 μm made of zinc sheet coating material 18 can be dried better.

[0060] Furthermore, the space required for the facilities to implement the method of the present invention is thus greatly reduced, limited to the size of the spindle 13 (considering that stations 23 and 23b can be a single station) and the size of the system for supporting and controlling the spray nozzle 19 and the IR lamp 28 (which can be constituted by the same spindle 13 in a single complete station 23 equipped with both the nozzle 19 and the lamp 28 with the shield 30).

[0061] The internal temperature of the wheel hub unit 1 is ultimately maintained at a relatively low value that will not cause any risk of damage.

[0062] Therefore, all the objectives of this invention have been achieved.

Claims

1. A method for coating an exposed surface (2) of a wheel hub assembly (1), the wheel hub assembly (1) comprising a rolling bearing (3), the rolling bearing (3) further comprising a relatively rotatable outer ring (4) and an inner ring (5) and corresponding first mounting flange (6) and second mounting flange (7) integrally constrained radially outward to the outer ring (4) and the inner ring (5), the first flange (6) being integrally constrained to the outer ring (4) and the second flange (7) being integrally constrained to the inner ring (5), characterized in that, The method includes the following steps: a) The fully assembled wheel hub assembly (1) is cantilevered onto the motorized first spindle (13), and the wheel hub assembly is inserted into the first spindle on one side of the first flange (6) until the first end (8) of the wheel hub assembly adjacent to the first flange (6) abuts against the annular shield (14) mounted on the radially outer side of the first spindle (13). b) Applying a layer (16) of zinc sheet coating material (18) to the first exposed surface (2) of the wheel hub assembly by means of an air spray nozzle (19), the first exposed surface (2) including at least one front surface (10) of the first flange (6) and a radially outer peripheral edge (11); rotating the wheel hub assembly (1) by means of the first spindle (13), and while rotating the wheel hub assembly (1), placing all of the nozzles (19) together or sequentially in front of the first exposed surface (2) at a predetermined distance from the first exposed surface (2); shielding the uncoated second exposed surface (12) of the wheel hub assembly by means of the annular shield (14) and by means of at least one shielding strip (20); c) The wheel hub assembly (1) is rotated by means of the same first spindle (13) or by means of a second spindle (13b) substantially the same as the first spindle, the wheel hub assembly (1) being integrally constrained angularly to the first spindle (13) or the second spindle (13b), such that the first end (8) of the wheel hub assembly (1) abuts against the same annular shield (14) or another identical annular shield (14) mounted radially outward of the first spindle (13) or the second spindle (13b), and while the wheel hub assembly (1) is rotating, the first exposed surface (2) is heated by means of IR lamps (28) by irradiation, the IR lamps (28) being placed together or sequentially in front of the first exposed surface (2) at a predetermined distance from the first exposed surface (2) until the layer (16) of the previously applied zinc sheet coating material (18) is fully cured.

2. The method according to claim 1, characterized in that, Step c) is performed using at least a pair of IR lamps (28) with a power of about 3000 watts and arranged on opposite sides of the first exposed surface (2) for a duration of no more than 480 seconds, preferably for a duration of 360 seconds.

3. The method according to claim 1 or 2, characterized in that, Step c is performed by rotating the wheel hub assembly (1) about its own axis of symmetry (A) at a speed of about 60 rpm by means of the first spindle (13) or the second spindle (13b).

4. The method according to any one of the preceding claims, characterized in that, The nozzle (19) and the IR lamp (28) are positioned in front of the first exposed surface (2) by moving the nozzle (19) and the IR lamp (28) relative to the first spindle (13) or the second spindle (13b) or by moving the first spindle (13) or the second spindle (13b) toward the nozzle (19) or the IR lamp (28).

5. The method according to any one of the preceding claims, characterized in that, The layer (16) of the coating material (18) made of zinc sheet is deposited on the first exposed surface (2) of the wheel hub assembly (1), the first exposed surface (2) including, in addition to the front surface (10) of the first flange (6) and the radial outer peripheral edge (11), at least one radial outer surface (17) of the outer ring (4) defining the first end (8) of the wheel hub assembly.

6. The method according to any one of the preceding claims, characterized in that, The at least one shielding strip (20) is stretched in the axial space between the first flange (6) and the second flange (7) to protect the second exposed surface (12) located on the second flange (7) and on the second end (21) of the wheel hub assembly opposite to the first end (8); the shielding strip (20) is preferably unwound from and wound around a pair of rotating reels (22) disposed on opposite sides of the first spindle (13).

7. The method according to any one of the preceding claims, characterized in that, During step b), the first spindle (13) rotates between about 120 rpm and about 150 rpm, and the zinc flake coating material (18) is sprayed from the nozzle (19) under an overpressure of about 0.45 bar to about 0.9 bar relative to atmospheric pressure, and preferably at a temperature between 10°C and 40°C; the zinc flake coating material (18) is continuously recirculated in hydraulic circuits (24) connected upstream and downstream of the nozzle to the nozzle (19).

8. The method according to any one of the preceding claims, characterized in that, During step c), the entire wheel hub assembly (1), except for the first exposed surface (2) of the wheel hub assembly, is shielded from the IR radiation beam (29) emitted by the IR lamp (28) by means of the annular shield (14) and by means of the heat shield (30) arranged between the IR lamp (28) and the second exposed surface (12) of the wheel hub assembly, the heat shield (30) preferably being laterally constrained to the IR lamp (28).

9. A wheel hub assembly (1) for a motor vehicle, comprising a rolling bearing (3), the rolling bearing (3) further comprising a relatively rotatable outer ring (4) and an inner ring (5) and corresponding first mounting flange (6) and second mounting flange (7) respectively directly or indirectly integrally constrained to the radially outer sides of the outer ring (4) and the inner ring (5), the wheel hub assembly comprising a first exposed surface (2) and a second exposed surface (12), the first exposed surface (2) comprising at least one front surface (10) of the first flange (6) and a radially outer peripheral edge (11), characterized in that, The first exposed surface (2) is coated with a layer (16) of zinc sheet coating material (18) made by the coating method according to any one of the preceding claims, and the layer (16) has a radial thickness between 9 micrometers and 35 micrometers.

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