Method for compacting an Anti-corrosion coating

Abstract

One aspect of the invention relates to a method for compacting (100) an anti-corrosion coating (110), characterized in that it comprises a step (101) of spraying water-soluble particles (130).

Description

TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of the protection of parts subjected to corrosion phenomena.

[0002] The technical field of the invention relates more particularly to the protection of steel parts by the application of a protective coating to various corrosive or oxidative anti-corrosion elements, such as an inorganic paint.

[0003] The invention has a particularly interesting application in the field of turbomachinery, especially for the protection of compressor shafts and turbine shafts of a turbomachine. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0004] Steels, particularly high-strength steels or highly alloyed steels, such as Maraging steels, are highly susceptible to corrosion. On these steels, corrosion primarily manifests as pitting on the surface.

[0005] Furthermore, the high mechanical stresses these parts are subjected to tend to increase corrosion. It is therefore essential to apply a protective coating to these parts to prevent corrosion and extend their lifespan.

[0006] In the field of turbomachinery, it is known to use as an anti-corrosion coating a paint based on a mineral or hybrid binder and metallic particles for the protection of turbine or compressor shafts.

[0007] Due to the presence of chromium trioxide in the composition of these commonly used mineral paints, their use is impacted by recent regulations.

[0008] Other mineral-based paints have therefore been studied as alternative paints to replace those containing chromium trioxide. All these paints have a composition based on a mineral or hybrid binder and metallic particles, such as aluminum. After application, these mineral- or hybrid-bound paints must undergo a high-temperature polymerization cycle to cure the paint film. A final specific requirement for the use of these paints is the compaction of the paint layer. This compaction brings the metallic particles into contact with the surface, making the paint layer dense and electrically conductive without compromising its physical integrity or cosmetic appearance. Through compaction, the paint acquires effective anodic sacrificial properties to combat corrosion.

[0009] Unlike chromium trioxide-based paints which do not necessarily require compaction, this compaction step is a crucial and mandatory step for chromium trioxide-free replacement paints, as this step guarantees the coating's good anti-corrosion properties.

[0010] This compaction step is conventionally carried out by corundum blasting (sandblasting), glass bead blasting, polishing, or heating. It is also known from document EP 1 598 444 A1 that this compaction step can be carried out using dry ice. This document thus discloses a method for compacting an anti-corrosion coating according to the preamble of independent claim 1.

[0011] During this compaction stage, the compaction media used (corundum or glass beads), which has a high hardness (between 8 and 9.5 on the Mohs scale), can become embedded in the surface of the paint layer and be released later, for example, during operation. This situation is particularly problematic when the parts coated with these paints are turbomachine components, such as turbine or compressor shafts, because the release of the compaction media during operation could damage certain turbomachine parts.

[0012] Therefore, in the field of turbomachinery, to avoid any risk of damage, it is common practice not to perform this compaction operation on certain sensitive parts, such as turbine or compressor shafts. This has the consequence of significantly reducing the anti-corrosion properties of the coatings.

[0013] Furthermore, when the paint layer is not compacted, it must be applied manually in two coats to minimize coating porosity, which increases application and part preparation time. In addition, controlling the thickness during this application is often tricky. SUMMARY OF THE INVENTION

[0014] In this context, the invention proposes a new method for compacting an anti-corrosion coating which overcomes the disadvantages mentioned above and increases the corrosion protection of parts while eliminating the problems of release of the compaction medium during the use of the parts.

[0015] To this end, the invention relates to a method of compacting an anti-corrosion coating comprising a step of projecting water-soluble particles based on sodium hydrogen carbonate and having a particle size between 70 µm and 200 µm.

[0016] In addition to the characteristics mentioned in the preceding paragraph, the compaction process according to the invention may have one or more additional characteristics from among the following, considered individually or in all technically possible combinations: The water-soluble particles projected during the projection stage have a hardness of less than 9 on the Mohs scale; the water-soluble particles projected during the projection stage have a density of approximately 2.2 g / cm3; the water-soluble particles projected during the projection stage incorporate an additive to prevent the agglomeration of the water-soluble particles with each other; the projection stage of water-soluble particles is carried out at a pressure of between 1.5 and 4 bar, and preferably 2 bar; the projection stage of water-soluble particles is carried out with two passes of projection of water-soluble particles; said two passes of projection of water-soluble particles are carried out with a projection angle of between 45° and 90° with respect to a substrate on which said anti-corrosion coating is applied;The said compaction process includes a rinsing step to remove water-soluble particle residues after spraying; the said compaction process is a process for compacting a paint based on metallic particles and a mineral or hybrid binder.

[0017] The invention also relates to a method for applying a surface treatment to a substrate characterized in that it comprises: a step of applying a first layer of paint based on metallic particles and a mineral or hybrid binder; a step of heating said support; a step of compacting said first layer of paint based on metallic particles and a mineral or hybrid binder according to the compaction process according to the invention.

[0018] The invention also relates to a method for applying a surface treatment to a substrate characterized in that it successively comprises: a step of applying a first layer of paint based on metallic particles and a mineral or hybrid binder; a first step of heating said support; a step of applying a second layer of paint based on metallic particles and a mineral or hybrid binder; a second step of heating said support; a step of compacting said layers of paint based on metallic particles and a mineral or hybrid binder according to the compaction process according to the invention.

[0019] Advantageously, the support is a metal piece.

[0020] Advantageously, the support is a piece made of high-alloy steel.

[0021] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0022] The figures are presented for illustrative purposes only and are in no way limiting to the invention. There figure 1 illustrates a synoptic diagram showing the main stages of the compaction process according to the invention. figure 2 is a simplified representation of a particle projection means used during the first stage of the compaction process according to the invention. figure 3 is a photograph taken using a scanning electron microscope illustrating the surface of a part coated with a mineral paint containing aluminum particles before compaction. figure 4 is a photograph taken using a scanning electron microscope illustrating the surface of the part coated with a mineral paint containing aluminum particles, as shown in the figure 4 after compaction by the compaction process according to the invention. The figure 5illustrates a synoptic diagram showing the different stages of applying an anti-corrosion coating to a turbomachine part.

[0023] Unless otherwise specified, the same element appearing on different figures has a unique reference. DETAILED DESCRIPTION

[0024] There [ Fig 1 ] illustrates a synoptic diagram showing the main steps of the compaction process 100 according to the invention.

[0025] The compaction process 100 according to the invention allows the compaction of an anti-corrosion coating 110 applied to a support 120, for example a steel part.

[0026] The compaction process 100 according to the invention is particularly interesting for compacting an anti-corrosion coating 110 applied to a part made of high mechanical strength steel, or high alloy steel.

[0027] The anti-corrosion coating 110 is, for example, a high-temperature mineral paint featuring a mineral or hybrid binder and metallic particles such as aluminum particles.

[0028] The compaction process 100 according to the invention is advantageously a compaction process for an anti-corrosion coating 110 of a turbomachine part 120.

[0029] The compaction process 100 according to the invention consists of projecting water-soluble particles 130 onto the anti-corrosion coating layer 110 to compact the latter and increase its anti-corrosion properties.

[0030] Advantageously, the particles 130 used in the compaction process 100 according to the invention are particles with a relatively low hardness, i.e. less than 9 on the Mohs scale, and preferably less than 4.

[0031] Thus, in a first step 101, the compaction process 100 according to the invention consists of projecting water-soluble particles 130 onto the anti-corrosion coating layer 110 of the treated part 120.

[0032] This projection step 101 is carried out via an ad hoc projection means 150 allowing water-soluble particles 130 to be projected under pressure.

[0033] There [ Fig 2 ] illustrates an example of a representation of a projection means 150 used for compacting the anti-corrosion coating 110 according to the invention.

[0034] The projection device 150 is, for example, a pressure or vacuum sandblaster. The sandblaster typically has a storage tank 151 containing the water-soluble particles 130 to be projected and a projection device 152 connected to said storage tank 151 via a supply hose 153.

[0035] The water-soluble particles 130 are, according to the invention, particles based on sodium hydrogen carbonate, also called sodium bicarbonate or baking soda. The water-soluble particles 130 based on sodium hydrogen carbonate advantageously have a hardness of 2.5 on the Mohs scale and a solubility of between 80 and 100 g / L in water at 20°C.

[0036] Water-soluble particles 130 have a size between 70 µm and 200 µm.

[0037] Water-soluble particles 130 based on sodium hydrogen carbonate have a density of approximately 2.2 g / cm3.

[0038] Optionally, an additive is added to the water-soluble particles 130 to prevent the particles 130 from clumping together during storage and / or projection.

[0039] The working pressure used for projecting the water-soluble particles 130 is advantageously in the order of 2 bar. This pressure is continuous and regulated at the projection device 152, for example via a pressure gauge (not shown) with a pressure adjustment mechanism.

[0040] The dosage of the projected quantity of water-soluble particles 130 is based on a fixed calibration (for example determined by the size of the projection nozzle) and on the pressure difference between the storage tank 151, storing the particles 130, and the working pressure used.

[0041] The water-soluble particles 130 are advantageously projected at an angle between 45° and 90° relative to the anti-corrosion coating 110 of the part 120 to be treated.

[0042] This projection step 101 may include one or more passes of projection of water-soluble particles 130. The different passes are carried out with the same projection angle or with a different projection angle (for example, one pass with an angle of 45° relative to the support and one pass with an angle of 90° relative to the support).

[0043] The compaction process 100 according to the invention may also optionally include a rinsing step 102 of the workpiece 120 to remove residues from the projection medium. This rinsing step 102 ensures the removal of residual water-soluble particles 130 by the solubility of sodium bicarbonate particles in water.

[0044] Advantageously, this rinsing step 102 is carried out with distilled water.

[0045] This rinsing step 102 is an optional step because, given the low hardness of the water-soluble particles 130 of sodium hydrogen carbonate (hardness of 2.5 on the Mohs scale), the water-soluble particles 130 are only slightly, or almost not, embedded in the anti-corrosion coating layer 110 and the particles are easily removed.

[0046] This rinsing step 102 is particularly important to ensure the removal of any water-soluble particles 130 embedded in the anti-corrosion coating layer 110, especially for sensitive parts such as turbine shafts or turbomachine compressor shafts.

[0047] Photographs taken using a scanning electron microscope show the densification of the anti-corrosion coating 110 after implementation of the compaction process 100 according to the invention.

[0048] There [ Fig 3] is a photograph taken using a scanning electron microscope illustrating the surface of a part coated with an aluminum-particle mineral paint before compaction.

[0049] There [ Fig 4 ] is a photograph taken using a scanning electron microscope illustrating the surface of the part coated with a mineral paint containing aluminum particles, as shown in the [ Fig 4 ] after compaction by the compaction process 100 according to the invention.

[0050] We notice on the [ Fig 4 that the aluminum particles that make up the mineral paint of the coating are no longer independent of each other and form a continuous surface. The results thus obtained by the applicant are similar to the results obtained by prior art compaction using glass beads or corundum.

[0051] After compaction, the 110 anti-corrosion coating typically has a uniform, glossy, and smooth appearance. The electrical resistance of the compacted coating is less than 5 ohms, and even less than 1 ohm. The thickness loss of the coating layer following the compaction process is minimal and less than 10 µm.

[0052] The compaction process 100 of an anti-corrosion coating 110 according to the invention allows: to bring the aluminum particles of mineral paints, based on a mineral binder and aluminum particles, into contact, used as an anti-corrosion coating; to densify the surface of the anti-corrosion coating; to make the electrical resistance of the coating less than 5 Ohms, or even less than 1 Ohm; to increase the corrosion and temperature resistance of steel parts; not to degrade the adhesion of the compacted paint.

[0053] The compaction process 10 of an anti-corrosion coating 110 by projection of water-soluble particles 130 according to the invention makes it possible to easily treat parts of complex geometry, of large dimensions.

[0054] The use of water-soluble particles 130, such as sodium bicarbonate particles, also provides a definite advantage during its handling and transport, due to its harmlessness and biodegradability.

[0055] The compaction process 100 described above fits perfectly into an overall surface treatment process of a steel part 120 by applying an anti-corrosion coating 110.

[0056] To this end, the invention also relates to a method for applying a surface treatment to a substrate 120, such as a steel part, comprising in particular: a step of applying a layer of mineral paint; a drying step; a step of compacting the layer of mineral paint according to the compaction process 100 described previously.

[0057] As an example, and with reference to the [ Fig 5 ], we will now describe a full range of applications of a surface treatment, such as an anti-corrosion coating 110 formed by a high-temperature mineral paint, on a steel part 120 of a turbomachine.

[0058] Thus, the application process 300 of a surface treatment to a turbomachine part 120 comprises: a step 301 of degreasing the surface of said part 120 to be treated; an optional step 302 of masking certain areas of part 120 that should not receive paint; a step 303 of sandblasting said part 120 to promote adhesion of the paint to the surface of the part to be treated; a step 304 of applying a first coat of mineral paint; a step 305 of desolvation and drying of said first coat of mineral paint; a step 306 of heating said part 120 (for example, a minimum of 30 minutes at 340°C) to polymerize said first coat of mineral paint; a step 307 of applying a second coat of mineral paint; a step 308 of desolvation and drying of said second coat of mineral paint; a step 309 of heating said part 120 (for example 30 min minimum at 340°C) to polymerize said second layer of mineral paint;a step 310 of compacting said paint layers by projecting water-soluble particles 130 according to the process 100 described previously; a step 311 of checking, for example, appearance, homogeneity, thickness, adhesion, etc.;

[0059] Advantageously, the turbomachine part is a turbine shaft or a compressor shaft.

Claims

1. Method for compacting (100) an anticorrosion coating (110) comprising a step (101) of projecting water soluble particles (130) characterised in that the water soluble particles (130) are based on sodium hydrogen carbonate and have a particle size comprised between 70 µm and 200 µm.

2. Method for compacting (100) an anticorrosion coating (110) according to claim 1, characterised in that the water soluble particles (130) projected during the projection step (101) have a hardness less than 9 on the Mohs scale.

3. Method for compacting (100) an anticorrosion coating (110) according to one of the preceding claims, characterised in that the water soluble particles (130) projected during the projection step (101) have a density of 2.2 g / cm3.

4. Method for compacting (100) an anticorrosion coating (110) according to one of the preceding claims, characterised in that the water soluble particles (130) projected during the projection step (101) incorporate an additive to avoid the agglomeration of the water soluble particles (130) with one other.

5. Method for compacting (100) an anticorrosion coating (110) according to one of the preceding claims, characterised in that the step (101) of projecting water soluble particles (130) is carried out at a pressure comprised between 1.5 bars and 4 bars, and preferentially at a pressure of 2 bars.

6. Method for compacting (100) an anticorrosion coating (110) according to one of the preceding claims, characterised in that the step (101) of projecting water soluble particles (130) is carried out with two passes of projecting water soluble particles (130).

7. Method for compacting (100) an anticorrosion coating (110) according to claim 6, characterised in that said two passes of projecting water soluble particles (130) are carried out with a projection angle comprised between 45° and 90° with respect to a support (120) on which said anticorrosion coating (110) is applied.

8. Method for compacting (100) an anticorrosion coating (110) according to one of claims 1 to 7, characterised in that said compaction method (100) comprises a rinsing step (102) to eliminate residues of water soluble particles (130) after projection.

9. Method for compacting (100) an anticorrosion coating (110) according to one of claims 1 to 8, characterised in that said compaction method (100) is a method for compacting a paint comprising metal particles and a mineral or hybrid binder.

10. Method for applying (300) a surface treatment on a support (120) characterised in that it comprises: - a step (304) of applying a first paint layer based on metal particles and a mineral or hybrid binder; - a step (306) of temperature adjustment of said support (120); - a step (310) of compacting said first paint layer based on metal particles and a mineral or hybrid binder according to the compaction method of one of claims 1 to 9.

11. Method for applying (300) a surface treatment on a support (120) according to claim 10 characterised in that it comprises successively: - a step (304) of applying a first paint layer based on metal particles and a mineral or hybrid binder; - a first step (306) of temperature adjustment of said support (120); - a step (307) of applying a second paint layer based on metal particles and a mineral or hybrid binder; - a second step (309) of temperature adjustment of said support (120); - a step (310) of compacting said paint layers comprising metal particles and a mineral or hybrid binder according to the compaction method of one of claims 1 to 9.

12. Method for applying (300) a surface treatment on a support (120) according to one of claims 10 to 11 wherein the support (120) is a metal part.

13. Method for applying (300) a surface treatment on a support (120) according to one of claims 10 to 12 wherein the support (120) is a part made of heavily alloyed steel.

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