Composition, intended to form a protective and / or sealing coating or adhesive for a substrate, based on a pre-ceramic silicon polymer and a nitric acid resistant filler, Process and Associated coated substrate.

Abstract

Composition, intended for forming a protective and / or sealing coating or adhesive for a substrate, based on a silicon preceramic polymer and a nitric acid-resistant filler, Process and Associated Coated Substrate. The invention relates to a composition, intended for forming a protective and / or sealing coating or adhesive for a substrate, comprising a mixture of the following constituents: - at least one silicon-based preceramic polymer precursor; - at least one nitric acid-resistant filler (HNO3); - optionally, at least one organic solvent; - optionally, at least one nitric acid pickling inhibitor and / or catalyst. Figure for the abstract: Fig. 2

Description

Title of the invention: Composition, intended to form a protective and / or sealing coating or adhesive for a substrate, based on a pre-ceramic silicon polymer and a filler resistant to nitric acid, Process and Associated coated substrate. technical field

[0001] The present invention relates to a composition intended to form a protective and / or sealing coating or adhesive for a substrate, in particular a metallic one.

[0002] The present invention also relates to a method of forming a protective coating or adhesive and / or sealing a substrate, as well as the substrate covered by the coating or adhesive obtained according to the method.

[0003] More particularly, the main objective of the invention is to obtain a protective and / or sealing coating or adhesive for a substrate, which is easy to implement, at a lower cost, which does not contain carcinogenic, mutagenic or toxic to reproduction (CMR) chemical agents and which has good protective or sealing performance, particularly in a harsh environment, particularly in an acidic environment, such as with nitric acid (HNO3).

[0004] Although described with reference to an application to a metallic pipe used for the transport of acidic fluids, in particular nitric acid (HNO3), the invention can be implemented for the protection of any metallic pipe, and more generally of any substrate, metallic or not, in particular subjected to a severe environment with corrosive fluid such as an acid. Previous technique

[0005] Metals such as stainless steels, aluminum alloys for example are materials used in containers or pipes for the transport or storage of acids.

[0006] These metals, although corrosion-resistant, are, over time, corroded by the very acids they carry / contain. Embrittlement of the metal, potentially leading to cracking or perforation, can be observed in industrial applications.

[0007] It is therefore necessary to protect these materials to increase the lifespan of the installations (supply pipes, tanks, basins) against acid attacks.

[0008] Oxidizing acids pose particular problems because the coating must be resistant to both acidic and oxidizing environments compared to inorganic and organic acids.

[0009] Commercial solutions have limited performance in terms of resistance to nitric acid corrosion, for example, or contain CMR chemicals, or can hardly be implemented in a constrained environment and are based on organic polymers.

[0010] The inventors have compiled an inventory of acid-resistant organic and inorganic coating solutions. A comprehensive overview of existing coatings for the chemical industry is provided in publication [1], particularly in Table 5 for ceramic coatings with their compositions in % by weight and in Tables 6 and 7 for commercial organic coatings.

[0011] Among these, the inventors focused on solutions that may be candidates to resist nitric acid HNO3.

[0012] Although not specifically mentioned for its resistance to acids such as HNO3, fluorosilicone, which has a temperature resistance between -65°C and 260°C, exhibits good chemical resistance to hydrocarbons, solvents, and chemical attack. This resin can be applied using a squeegee or spatula. However, application methods are limited by its high viscosity. The curing time is not adjustable since fluorosilicone is a single-component compound.

[0013] Epoxy vinyl ester resins are advantageous for applications in oxidizing acidic environments because certain groups near the ester bond act as steric hindrances, thus limiting contact between diffusing molecules. This steric effect also prevents hydrolysis products from escaping the reaction site, thereby restricting reactions to the surface only. An epoxy vinyl ester resin is usually more fluid than a fluorosilicone and can be more easily applied with various deposition tools. The curing time is adjustable by adding additives and can range, for example, from 30 minutes to 1 hour, depending on the manufacturer's formulations. However, these epoxy vinyl ester resins contain styrene, a CMR solvent.Furthermore, the additives required for crosslinking—co-naphthenate (a crosslinking promoter at room temperature), cumene hydroperoxide (a crosslinking initiator), and 2,4-pentandione (a crosslinking retarder)—are also harmful. According to publicly available data, type 470 vinyl ester epoxy resins are resistant to nitric acid at concentrations between 0 and 5% (0-0.75 mol / L) up to an application temperature of 80°C, but only down to 40°C at concentrations of 30 to 35% (5.5 to 6.5 mol / L).

[0014] Epoxy resins containing titanium fillers, hereinafter epoxy 1, and in the form of a putty are used for precision repairs on equipment Critical areas subjected to stress, protection of new surfaces against erosion and corrosion, and repair of hollows. They can be applied using a putty knife, trowel or spatula.

[0015] Epoxy resins containing ceramic fillers, hereinafter referred to as epoxy 2, having a viscosity suitable for spray application are used, for example, for sealing and protecting new equipment exposed to erosion and corrosion, protecting pump bodies, compressor blades, spool valves, water boxes, and fan blades. The viscosity of epoxy 2 resins is 9000 cPs at 21°C. These epoxy 2 resins can be spray-applied in thicknesses between 400 and 600 µm in a single pass. These epoxy 2 resins are mixed with their respective hardeners using a spatula with a resin / hardener mass ratio of 4.3:1 and 2.6:1 respectively, according to the supplier's recommendations.

[0016] According to the literature, these epoxy resins 1 and epoxy 2 can be resistant to nitric acid at a concentration of 10% (1.7 mol / L) for 30 days under immersion at 21°C and after a curing time of 7 days at room temperature. Their resistance to nitric acid is weak above 20% (3.6 mol / L). They are suitable for splash contact only, with immediate cleanup.

[0017] Patent EP1851772 B1 discloses a resin, marketed under the name Hetron 197, specifically developed for sealing cracks in spent nuclear fuel reprocessing facilities, where numerous metallic devices are used to convey or temporarily store materials containing nitric acid. This resin contains accelerator, inhibitor, and catalyst additives that control the resistance to nitric acid and the lifespan of the formulation, allowing it to be applied under specific conditions without premature crosslinking problems. As mentioned in the patent, while this resin can be used in HNO3 conditions at a concentration of 6M, it is diluted with styrene, a solvent that is extremely harmful to health.

[0018] Apart from the disadvantage of the cost of manufacturing or depositing existing coatings, the inventors concluded that none of them seemed to meet the need for both high protection or sealing performance, without CMR products, ease of implementation with conventional techniques and a long service life.

[0019] A particular need is to find a coating which can both exhibit resistance to nitric acid in a wide range of concentrations, typically from 0.01% (0.1M) to 53% (10M), for a period of more than 24h, over a wide temperature range, typically between 20 and 120°C, and without CMR products.

[0020] The object of the invention is to meet at least partially this need(s). Description of the invention

[0021] To this end, the invention relates, in one of its aspects, to a composition intended to form a protective and / or sealing coating or adhesive for a substrate, comprising a mixture of the following constituents:

[0022] - at least one silicon-based preceramic polymer precursor;

[0023] - at least one charge resistant to nitric acid (HNO3);

[0024] - where appropriate, at least one organic solvent;

[0025] - where appropriate, at least one nitric acid pickling inhibitor and / or a catalyst.

[0026] Silicon-based preceramic polymer precursor

[0027] The preceramic polymer precursor is a molecular precursor that is heat-treated, generally at a temperature of up to 400°C, to lead, after polymerization, to a cross-linked polymer. Depending on the nature of the preceramic polymer, cross-linking may also take place at ambient temperature and humidity.

[0028] The preceramic polymer precursor, in solid or liquid form, is soluble in organic solvents or can be melted at temperatures below 150°C. By adding solvent or by melting, depending on the temperature, it is possible to adjust the viscosity in order to shape these materials using various techniques employed in the field of plastics processing, such as extrusion, injection molding, casting, spraying, painting tools, thermopressing, and heat guns.

[0029] Preferably, the preceramic polymer precursor is chosen from among a polysiloxane, a polysilsesquioxane, a polysilazane, a polycarbosilazane, a polycarbosiloxane, a polycarbosilane, a polyborosiloxane, a polyborolazane, a polysilylcarbodiimide, or a mixture thereof. Preferably, the preceramic polymer precursor is a polysiloxane precursor.

[0030] Advantageously, the preceramic polymer precursor has a content of between 40 and 95% vol, expressed as a volume percentage, preferably between 40 and 70%. Nitric acid (HNO3) resistant filler

[0031] It is possible to add a wide variety of fillers to modulate the properties of the resulting coating or adhesive, such as chemical resistance properties, variation of thermal expansion, thermal properties,...), to limit shrinkage and to increase the deposited thicknesses.

[0032] Incorporating a filler into a protective coating and / or sealant can greatly improve its anti-corrosion performance by decreasing porosity and increasing the tortuous pathway for corrosive species. This can also increase the bond strength between the coating and the substrate and reduce delamination of the coating from the substrate.

[0033] Advantageously, the filler is chosen from sapphire (α-Al2O3), zirconia (ZrO2), and silicon carbide (SiC). These filler materials are the most resistant to nitric acid at a concentration of 60% (1.3 mol / L) at a temperature of 90°C.

[0034] According to an advantageous embodiment, the silicon carbide (SiC) has a content of between 5 and 60%, expressed as a volume percentage. Above 60%, the preceramic polymer content is insufficient to coat the filler particles and obtain a dense formulation after drying. The resulting porosity would allow the acid to penetrate the coating / adhesive and come into contact with the substrate. The particles range in size from nanometers to several tens of micrometers. The choice of size also depends on the desired thicknesses.

[0035] Finally, the filler particles can have a spherical, angular, or lamellar morphology. It is preferable to add particles that will increase the tortuous path of the corrosive species and therefore to work with angular or lamellar fillers. Organic solvent

[0036] The organic solvent is a solvent capable of dissolving the preceramic polymer precursor in its solid state. Thus, the filler and the precursor are dispersed, particularly in solution or suspension, within the organic solvent. This organic solvent therefore advantageously facilitates the mixing of the various components of the composition and thus results in a homogeneous mixture.

[0037] For a liquid preceramic polymer precursor, the organic solvent is added to modify the viscosity of the mixture. Generally, the quantity and nature of the solvent are variables adjusted to make the viscosity of the composition compatible with the processing method and the thickness to be deposited.

[0038] The organic solvent also makes it easier to apply to the surface of the substrate, in particular metallic.

[0039] Preferably, the organic solvent is methyl ethyl ketone (MEC or butanone) or acetone, or ethanol.

[0040] This may be a mixture marketed under the trade name DIESTONE® DLS. This mixture is a solvent-based composition with controlled volatility and low odor, free from chlorinated hydrocarbons. This composition offers maximum safety because it does not contain any teratogenic or carcinogenic constituents, toluene and ethylene glycol ethers.

[0041] Advantageously, the organic solvent has a content of between 5 and 90% by mass, preferably between 20 and 60% by mass.

[0042] The quantity of solvent is dependent on the deposition process and the desired final thickness. Catalyst

[0043] The temperature and curing time of a coating / adhesive according to the invention can be controlled. In fact, the curing temperature can be reduced by 50 to 100°C by adding one or more catalysts to the composition. This allows adaptation to the thermal constraints of the environment in which the substrate to be coated and / or sealed is and / or will be exposed over time.

[0044] Advantageously, the catalyst is chosen from a metallic catalyst, preferably AlC13 or MnC13, or CrC13, a peroxide, a coordination compound based on aluminium, chromium or platinum, a thermal catalyst, preferably a mixture of cyclohexanone peroxide and cobalt(II) naphthenate, triethanolamine, tetrabutylammonium acetate, titanium butoxide or aluminium acetylacetonate.

[0045] An advantageous coordination compound is the Karstedt catalyst.

[0046] The catalyst(s) are to be adapted according to the preceramic polymer identified for the precursor.

[0047] For example, for the polysiloxane marketed under the name SILRES® MK, the catalysts offered by the manufacturer are either "Wacker catalyst K83" or triethanolamine. The catalyst(s) are preferably added in proportions of between 0.1% and 10% by weight, advantageously between 2% and 5%. This pre-ceramic polymer is crosslinked up to 300°C for 30 to 60 minutes. The addition of a catalyst allows the temperature to be lowered to 150°C with crosslinking times of between 5 and 135 minutes, according to supplier data. These limits can, however, be modified if complete crosslinking is not required for the application, and therefore the time and temperature can be reduced or increased depending on the intended process for shaping the coating or adhesive. Nitric acid pickling inhibitor

[0048] The inhibitor is advantageously chosen from a mixture of thiourea and sodium sulfide (Na2S), a mixture of hydrazine (C8H7N) and ammonium thiocyanate (NH4SCN) or Na2S, thiosulfate, aniline chloride, potassium thiocyanate, potassium dichromate, alkaloids, benzoquinone. Additives

[0049] Mesoporous inorganic particles can also be added to improve the corrosion resistance of a coating or adhesive according to the invention, such as cerium-enriched zeolite microparticles, ZrO2 nanoparticles, CaCO3, CeMo, TiO2, and Mn2O3 particles. Preferably, these inorganic particles are added to the composition in a proportion of between 0.1 and 15%, depending on the desired formulation.

[0050] The invention also relates to a method for forming a protective coating on a substrate, comprising the steps of:

[0051] i / provide a substrate;

[0052] ii / to produce a formulation so as to obtain a composition according to one of the preceding claims;

[0053] iii / carry out a deposition in ambient air of at least one layer of the composition on the substrate;

[0054] iv / heat treatment to obtain crosslinking of the polymer of each layer of composition carried out according to step iii / , in order to obtain the coated substrate.

[0055] According to a first alternative, step ii / is a liquid formulation.

[0056] Step iii / of deposition is preferably carried out according to a technique chosen from spraying, strip casting, centrifugal coating, dip coating, extrusion in particular by means of a syringe, 3D printing, vacuum printing.

[0057] The deposition can be carried out in one or more passes depending on the thicknesses.

[0058] According to a second alternative, step ii / is a dry formulation.

[0059] According to this second alternative, step ii / successively comprises a liquid formulation, a drying, a reduction into the form of a powder.

[0060] Advantageously, step ii / successively comprises mixing the silicon-based preceramic polymer precursor(s) with the nitric acid (HNO3) resistant filler(s), at a temperature above the melting temperature of the precursor or the highest of the precursors.

[0061] Advantageously, the deposition step iii / is carried out using a heating application technique, in particular by means of a heated gun or syringe.

[0062] Preferably, steps iii / and iv / are carried out so as to form a coating or adhesive 10 µm to 5 cm thick on the substrate.

[0063] Preferably, steps iii / and iv / are carried out so as to seal a hole or a crack.

[0064] According to an advantageous embodiment, step iii / of the heat treatment is carried out at a temperature below 400°C. Thus, the heat treatment can be a simple baking at a temperature allowing the polymerization of the preceramic polymer precursor, for example at 200°C (180 to 300°C), under air for 30 minutes to 1 hour.

[0065] The invention also relates to a substrate coated with a protective coating or a protective and / or sealing adhesive that can be obtained according to the process as previously mentioned.

[0066] The constituent material can be a metal or a metallic alloy chosen from a base alloy Fe, Al, Ni, Cu, Mo, Zr and their alloys.

[0067] According to an advantageous embodiment, the constituent material is steel, cast iron or stainless steel or Ni-based superalloy, preferably a stainless steel selected from one of the grades 304, 316, 316L, 316 LN or 321.

[0068] The invention also relates to the use of a substrate as mentioned above in an environment likely to contain at least one acid, in particular nitric acid (HNO3), typically at a concentration of 0.1 to 10 mol / L, perchloric acid, hydrobromic acid, sulfuric acid, or chromic acid. In this use, the acid may be up to its boiling point.

[0069] The composition according to the invention can be applied to any substrate, in particular metallic and which can take various and varied forms, such as a metal container, a tube, a pipe, an internal surface of equipment used for example in petrochemicals, such as a pump, a valve, a tube, a pipe, a metal equipment.

[0070] The invention essentially consists of a composition intended to form a protective and / or sealing coating or adhesive for a substrate, comprising a mixture of a silicon-based preceramic polymer precursor, a nitric acid (HNO3) resistant filler, and optionally an organic solvent, advantageously supplemented by at least one nitric acid pickling inhibitor and / or a catalyst.

[0071] In conclusion, a composition according to the invention offers numerous major advantages over compositions for protective coatings according to the prior art, among which we can mention: - Proven protection and sealing performance even in harsh environments, particularly with acidic fluids such as nitric acid with which a metallic substrate may come into contact, especially when in the form of a pipe transporting these acidic fluids, - a long lifespan, - Ease of implementation and lower deposition costs, due to the possibility of using standard ambient air deposition techniques, useful for maintenance and / or sealing of equipment or metal parts in various forms in different fields such as nuclear, chemical, agrochemical...

[0072] Other advantages and features of the invention will become clearer from the detailed description of examples of implementation of the invention given by way of illustration and not limitation with reference to the following figures. Brief description of the drawings

[0073] [Fig-1] [Fig. 1] is a photographic reproduction of a coating on a metallic support, obtained by deposition according to a strip casting technique of a composition according to the invention.

[0074] [Fig.2] [Fig.2] is an image obtained by secondary electron scanning electron microscopy (SEM) of a section of a metallic substrate on which a composition according to the invention has been deposited by tape casting.

[0075] [Fig.3] [Fig.3] illustrates in the form of plots the evolution of different materials including samples obtained according to the invention, in a bath of HNO3 acid at a concentration of 6 M, at a temperature of 80°C, without renewal of the bath.

[0076] [Fig.4] [Fig.4] illustrates in the form of plots the evolution of different materials including a sample obtained according to the invention, in a bath of HNO3 acid at a concentration of 6 M, at a temperature of 80°C, with renewal of the bath. Detailed description

[0077] Throughout this application, the terms "above," "below," "upper," and "lower" are to be understood by reference to the layers deposited on a substrate according to the invention. Thus, a protective coating obtained from a composition according to the invention is directly above a substrate to be protected. Example 1 according to the invention:

[0078] The inventors have carried out the production of a protective and / or sealing coating for a metallic substrate.

[0079] They first proceeded to prepare a composition intended to form such a coating in the form of a resin.

[0080] To do this, they produced a formulation by mixing the following constituents, with the contents expressed as volume percentages, indicated in Table 1 below.

[0081] [Tables 1] Constituent Volume Percentage Precursor of a preceramic polymer marketed under the trade name SILRES® MK 27 SiC powder filler 27 Organic solvent marketed under the trade name DIESTONE® 46

[0082] The preceramic polymer precursor was solubilized in the solvent and then the SiC powder was added and mixed.

[0083] Once the composition was made by homogenizing the formulation, it was applied by pouring in a strip using a squeegee, of said composition onto a stainless steel substrate.

[0084] Then, this coated plate was polymerized and dried and a heat treatment was carried out to obtain cross-linking of the coating polymer.

[0085] The final thickness of the coating is approximately 200 pm. Example 2 according to invention #:

[0086] The inventors carried out the production of another protective and / or sealing coating for a metallic substrate, as in example 1 by solvent means.

[0087] They first proceeded to prepare a composition intended to form such a coating in the form of a resin.

[0088] To do this, they produced a formulation by mixing the following constituents, with the contents expressed as volume percentages, indicated in Table 2 below.

[0089] [Tables2] Constituent Volume Percentage Precursor of preceramic polymer marketed under the trade name SILRES® MK 27 Filler of SiC powder, and ZnO-based glass frit 25.5 1.5 Organic solvent marketed under the trade name DIESTONE® 46

[0090] The preceramic polymer precursor was solubilized in the solvent and then the SiC powder mixed with the ZnO-based glass frit was added and mixed.

[0091] Once the composition was made by homogenizing the formulation, it was applied by pouring in a strip using a squeegee, of said composition onto a stainless steel substrate.

[0092] Then, this coated plate was polymerized (with a solvent evaporation step before or at the same time) and a heat treatment was carried out to obtain crosslinking of the coating polymer.

[0093] The final thickness of the coating is approximately 200 pm.

[0094] Comparative example 1: a known vinyl ester epoxy resin was deposited on a stainless steel substrate.

[0095] Comparative example 2: a known fluoro silicone resin was deposited on a stainless steel substrate.

[0096] Adhesion tests:

[0097] The inventors carried out pull-off tests for the coatings according to examples 1 and 2 of the invention and comparative examples 1 and 2.

[0098] The adhesion tests are carried out as follows: - A stud is glued onto the surface of the coating using a cyanoacrylate-type adhesive (for example). - Once glued, pull on this pad until it is pulled away. Pulling can occur between the substrate and the coating, or between the coating and the adhesive, or even within the coating itself, with one part remaining glued to the substrate and another part being glued to the pad.

[0099] The resin according to comparative example 1 has an adhesive break. It remains bonded to the substrate with a pull-out stress between 2 and 4 MPa.

[0100] The resin according to comparative example 2 demonstrates superior coating / substrate adhesion to adhesive / coating adhesion.

[0101] The fluorosilicone resin is however weakly adherent since it detaches at a stress of less than IMPa.

[0102] The resins according to Examples 1 and 2 of the invention have a cohesive failure, namely a fracture within the coating. The resin according to Example 1 of the invention is the one with the highest pull-out stress, which can reach 12 MPa.

[0103] Fig. 2 shows the interface between the microstructure of the protective coating 10 obtained according to example 2, and the stainless steel substrate 1 on which it was deposited directly. Example 3 according to the invention:

[0104] The inventors carried out another protective and / or sealing coating for a metallic substrate, but by dry means.

[0105] They first proceeded to prepare a composition intended to form such a coating in the form of a resin.

[0106] To do this, they produced a formulation by mixing the following constituents, with the contents expressed as volume percentages, indicated in Table 3 below.

[0107] [Tables3] Constituent Volume Percentage Precursor of preceramic polymer marketed under the trade name SILRES® MK 27 SiC powder filler 27 Organic solvent marketed under the trade name DIESTONE® 46

[0108] The preceramic polymer precursor was solubilized in the solvent and then the SiC powder was added and mixed.

[0109] Once the composition was achieved by homogenizing the formulation, it was dried and then the dried layer was ground to obtain a powder.

[0110] This powder was thermo-pressed at a temperature above the melting temperature of the preceramic polymer precursor, so as to obtain cylindrical pellets.

[0111] Then, a heat treatment was carried out to obtain cross-linking of the polymer of these pellets.

[0112] Each of the cylindrical pellets ultimately has a diameter of 30 mm and a height of 2.5 mm: Nitric acid resistance tests#:

[0113] The resin according to example 2 of the invention and the pellets according to example 3 of the invention are immersed in a bath of concentrated nitric acid at 6mol / L at a temperature of 80°C for a period of 15 days, without renewal of acid.

[0114] Fig. 3 illustrates the evolution of these pellets compared to a resin according to comparative example 1 and a resin according to comparative example 2, immersed under the same conditions.

[0115] It therefore appears that: - the resin according to comparative example 1 is totally dissolved after 24 hours in nitric acid and is therefore not resistant under these conditions; - the resin according to comparative example 2 behaves identically to the resin according to example 2 of the invention after 15 days of immersion. However, it was observed that the adhesion of the resin according to comparative example 2 is weak on the metallic substrate; - the resin according to comparative example 1 and the pellets according to example 3 of the invention behave identically and seem equally interesting for resistance to this acidic environment.

[0116] The tests carried out (adhesion, resistance to nitric acid) demonstrate that coatings according to the invention on a metallic substrate exhibit both good density, very good adhesion and no reaction to HNO3 acid.

[0117] The invention is not limited to the examples just described; in particular, features of the illustrated examples can be combined in unillustrated variants.

[0118] Other variants and embodiments may be envisaged without departing from the scope of the invention. List of cited references

[0119] [1]: Mpller, VB, Dam-Johansen, K., Frankær, SM et al. ^Acid-resistant organic coatings for the Chemical industry: a review." J Coat Technol Res 14, 279-306 (2017). https: / / doi.org / 10.1007 / sll998-016-9905-2

Claims

Demands

1. Composition, intended to form a protective and / or sealing coating or adhesive for a substrate, comprising a mixture of the following constituents: - at least one silicon-based preceramic polymer precursor; - at least one nitric acid (HNO3) resistant filler; - where applicable, at least one organic solvent; - where applicable, at least one nitric acid pickling inhibitor and / or catalyst.

2. Composition according to claim 1, the preceramic polymer precursor being selected from a polysiloxane, a polysilsesquioxane, a polysilazane, a polycarbosilazane, a polycarbosyloxane, a polycarbosilane, a polyborosiloxane, a polyborolazane, a polysilylcarbodiimide or a mixture thereof.

3. Composition according to claim 1 or 2, the preceramic polymer precursor having a content of between 40 and 95%, expressed as a volume percentage, preferably between 40 and 70%.

4. Composition according to any one of the preceding claims, the filler being selected from sapphire (a-Al2O3), zirconia (ZrO2), silicon carbide (SiC).

5. Composition according to claim 4, silicon carbide (SiC) having a content between 5 and 60%, expressed as a volume percentage.

6. Composition according to any one of the preceding claims, the organic solvent being selected from methyl ethyl ketone (MEK or butanone), acetone, or ethanol.

7. Composition according to any one of the preceding claims, the organic solvent having a content of between 5 and 90% by mass, preferably between 20 and 60% by mass.

8. Composition according to any one of the preceding claims, the nitric acid pickling inhibitor being selected from a mixture of thiourea and sodium sulfide (Na2S), a mixture of hydrazine (C8H7N) and ammonium thiocyanate (NH4SCN) or Na2S, thiosulfate, aniline chloride, potassium thiocyanate, potassium dichromate, alkaloids, benzoquinone.

9. Composition according to any one of the preceding claims, the catalyst being selected from a metallic catalyst, preferably A1C13 or MnCl3, or CrCl3, a peroxide, a coordination compound based on aluminium, chromium or platinum, a thermal catalyst, preferably a mixture of cyclohexanone peroxide and cobalt(II) naphthenate, triethanolamine, tetrabutylammonium acetate, titanium butoxide or aluminium acetylacetonate.

10. A method for forming a protective and / or sealing coating or adhesive on a substrate, comprising the steps of: i / providing a substrate; ii / preparing a formulation to obtain a composition according to one of the preceding claims; iii / carrying out a deposition in ambient air of at least one layer of the composition on the substrate; iv / heat treatment to obtain crosslinking of the polymer of each layer of composition carried out according to step iii / , in order to obtain the coated substrate.

11. The method according to claim 10, step ii / being a liquid formulation.

12. The method according to claim 11, the deposition step iii / being carried out according to a technique selected from spraying, strip casting, centrifugal coating, dip coating, extrusion in particular by means of a syringe, 3D printing, vacuum printing.

13. The process according to claim 10, step ii / being a dry formulation.

14. A process according to claim 13, step ii / comprising successively a liquid formulation, a drying, a reduction to the form of a powder.

15. The process according to claim 13, step ii / successively comprising mixing the silicon-based preceramic polymer precursor(s) with the nitric acid (HNO3) resistant filler(s), at a temperature above the melting temperature of the precursor or the highest of the precursors.

16.

17.

18.

19.

20.

21.

22. A method according to any one of claims 13 to 15, the deposition step iii being carried out according to an application technique with heating, in particular by means of a heated gun or syringe. A method according to any one of claims 10 to 16, steps iii / and iv / being carried out so as to form a coating or adhesive 10 µm to 5 cm thick on the substrate. A method according to any one of claims 10 to 17, wherein steps iii / and iv / are carried out so as to seal a hole or crack. Substrate coated with a protective and / or sealing coating or adhesive, which can be obtained according to the process according to one of claims 10 to 18. Substrate according to claim 19, the constituent material of which is a metal or a metallic alloy selected from a base alloy Fe, Al, Ni, Cu, Mo, Zr and their alloys. Substrate according to claim 20, the constituent material being a steel, a cast iron or a stainless steel or a Ni-based superalloy, preferably a stainless steel selected from one of the grades 304, 316, 316L, 316LN or 321. Use of a substrate according to any one of claims 19 to 21 in an environment likely to contain at least one acid, in particular nitric acid (HNO3), typically at a concentration of 0.1 to 10 mol / L at a temperature between 20 and 200°C, perchloric acid, hydrobromic acid, sulfuric acid, chromic acid

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