ANTI-CORROSION COATING COMPOSITION IN AQUEOUS DISPERSION

Abstract

The present invention relates to an anti-corrosion coating composition for metal parts based on particulate metal in aqueous dispersion comprising a mixture of monomers comprising silane, at least one silicate and at least one titanate.

Description

Title of the invention: ANTI-CORROSION COATING COMPOSITION IN AQUEOUS DISPERSION

[0001] The subject of the present invention is an anti-corrosion coating composition for metal parts based on particulate metal in aqueous dispersion comprising a mixture of monomers comprising silane, at least one organic silicate and at least one titanate.

[0002] State of the art

[0003] The environmental context of recent years has led to a need to reduce the carbon footprint of products regardless of their field of use. Coatings rich in flake zinc in aqueous phase (water-based) are known to present a positive image from an environmental point of view compared to 100% solvent-based products, but to obtain an equivalent level of anti-corrosion performance they must undergo a baking process of 310°C instead of approximately 240°C for solvent-based products; this considerably increases carbon equivalent emissions. In addition, the international context in the energy sector, in particular increases in energy prices and fuel shortages, is pushing manufacturers to rethink their production methods towards increasingly less energy-intensive solutions.

[0004] Patent EP1713869 filed under the name Dacral relates to the composition of an anti-corrosion coating for metal parts based on particulate metal in an aqueous dispersion comprising titanium and / or compatible organic zirconate in aqueous phase or in organic phase, possibly a silane-based binder, and water, however the baking temperature must be 310°C to obtain good anti-corrosion performance.

[0005] Patent US4224213 filed under the name COOK PAINT & VARNISH CO relates to the use of alkyl silicate and alkyl titanate to obtain a coating rich in zinc powder. In this patent, the composition is free of water and the film will form by crosslinking of the monomers in the presence of atmospheric humidity as a reaction initiator.

[0006] Patent KR101541046 filed under the name Zincotec relates to a zinc-rich coating combining silane, titanate, alkali silicate, water and particulate metal and whose composition comprises, for example, only 20.9 to 35% water and whose cooking temperature must be 310°C to obtain good anti-corrosion performance.

[0007] There is therefore a need for an anti-corrosion coating composition produced in a less polluting manner and comprising few VOCs (volatile organic compounds) which retains its anti-corrosion properties via its sacrificial power. Summary of the invention

[0008] After years of work and surprisingly, the inventors have succeeded in producing an anti-corrosion coating composition for metal parts based on a particulate metal in aqueous dispersion having a lower ecological impact than existing coating compositions because it makes it possible to produce a coating with a coating baking temperature of less than 310°C while retaining its anti-corrosion properties. In addition, the composition according to the invention comprises very few co-solvents and therefore a VOC (volatile organic compounds) level of less than 7%, preferably less than 5%.

[0009] The invention consists of the use of an aqueous organo-mineral sol-gel binder, in which the ratio of silane / silicate / titanate monomers surprisingly makes it possible to obtain crosslinking at low temperature while maintaining a long lifetime. The formulation parameters as well as the raw materials can also be optimized to obtain a formulation containing very few VOCs (<7%), crosslinking at low temperature (220°C) and making it possible to obtain cathodic protection of the film against corrosion at this same baking temperature of 220°C. This formulation can be free of methanol, and of CMR class raw materials.

[0010] The present invention therefore makes it possible to reduce the baking temperature of an anti-corrosion coating composition for metal parts by 90°C compared to compositions present on the market and thus to drastically reduce the energy consumed, and therefore the energy cost of the process. The installations can also be equipped with less powerful ovens, which makes it possible to reduce the amounts invested in these installations. The quantity of VOCs released and especially of degradation products is very significantly reduced (from -25% to less than 7%, preferably less than 5% for VOCs). The ecological and economic impacts are therefore very positive. Detailed description of the invention

[0011] The subject of the present invention is an anti-corrosion coating composition for metal parts based on a particulate metal in aqueous dispersion comprising in the following proportions (percentages by weight): - Between 2 and 50% of a mixture of monomers comprising silane, at least one silicate and at least one organic titanate; - Between 10 and 40% of at least one particulate metal or a mixture of particulate metals; - water: qsp 100%; characterized in that said mixture of monomers comprises in the following proportions (percentages by weight): - Between 40 and 70%, preferably between 40 and 60%, more preferably between 50 and 60% by weight of silane; - Between 10 and 40%, preferably between 15 and 30%, more preferably between 20 and 30% by weight of at least one silicate; and - Between 10 and 40%, preferably between 15 and 30%, more preferably between 15 and 25% by weight of at least one titanate.

[0012] The silicate may be an organic silicate of formula Si(OR)4 in which R1, R2, R3 and R4 independently represent an optionally substituted C1-C8 alkyl radical, preferably tetraethyl orthosilicate (TEOS) of formula Si(OEt)4.

[0013] The titanate may be chosen from the group consisting of organic titanates compatible in the organic phase and organic titanates compatible in the aqueous phase.

[0014] For the purposes of the present invention, the expression "compatible titanate(s) in organic phase" means any organic titanate which is not compatible with water, i.e. with strong reactivity in an aqueous composition and which is also sensitive to humidity and water (hydrolysis reaction).

[0015] For the purposes of the present invention, the expression "aqueous-phase compatible titanate(s)" means any titanate compatible with water, i.e. soluble or emulsifiable or dispersible in an aqueous composition. These are generally organic titanates which have been stabilized by chelation. They are also called "chelated (organic) titanate(s)". Organic-phase compatible organic titanates can be used in anhydrous compositions as catalysts, crosslinking agents, surface treatment agents, adhesion promoters or anti-corrosion agents.

[0016] The compatible titanates in the organic phase are advantageously CrC8 tetraalkyl titanates which can be represented by the following formula (I):

[0017] [Chem.l] R1 O R4^O™7|Ï -o—R2 O R3

[0018] in which R1, R2, R3 and R4 independently represent a C1-C8 alkyl radical, optionally substituted. The C1-C8 tetraalkyl titanate is advantageously

[0019]

[0020]

[0021] selected from the group consisting of tetraethyltitanate (TET, Ti(OC2H5)4), tetra-nbutyltitanate (TnBT, Ti(OC4H9), tetraisopropyltitanate (TPT, Ti[(OCH(CH3)2]4) and octyleneglycoltitanate (OGT, TI(O2C8Hi7)4), as well as mixtures thereof. Organic titanates compatible in the organic phase can also be organic titanates in chelated form that are not compatible with water. Examples of organic titanates in chelated form that are not compatible with water (compatible in the organic phase) include those marketed by Dorf Ketal under the name TYZOR® AA (acetylacetonate titanium), TYZOR® DC (diisopropoxy-bisethylacetoacetato titanate). The compatible titanates in aqueous phase are advantageously chelated titanates, which can be represented by the following general formula (II): [Chem 2]

[0022]

[0023]

[0024] in which R and R' independently represent a C 1 -C 10 alkyl radical, optionally substituted, X and X' independently represent a functional group comprising an oxygen or nitrogen atom, and Y and Y' independently represent a hydrocarbon chain having 1 to 4 carbon atoms. X and X' advantageously represent an amino or lactate radical. The organic titanate in chelated form compatible in aqueous phase is advantageously chosen from the group consisting of triethanolamine titanates (TYZOR© TE and TEP marketed by Dorf Ketal). As examples of organic titanates in chelated form compatible in aqueous phase, we can also cite those marketed by Dorf Ketal under the name TYZOR® TA (alkanolamine titanate in chelated form) and TYZOR® LA (chelate of titanate and lactic acid). In some embodiments, the organic titanate is selected from the group consisting of tetraethoxytitanate, tetraisopropoxytitanate, tetrabutoxytitanate, and mixtures thereof, preferably tetraethoxytitanate (TET). The particulate metal or mixture of particulate metals in the coating composition may be selected from the group consisting of metallic pigments such as aluminum, manganese, nickel, titanium, stainless steel, zinc, their alloys, and mixtures thereof. The particulate metal is advantageously selected among zinc and aluminum, as well as their alloys and their mixtures or their alloys with manganese, magnesium, tin or silicon.

[0025] The particulate metal present in the composition is advantageously in powder form, of different homogeneous or heterogeneous geometric structures, in particular spherical, lamellar, lenticular or other specific shapes. The particulate metal advantageously has a particle size of less than 100 qm, even more advantageously less than 40 qm.

[0026] Where the particulate metal is an alloy or mixture of zinc and aluminium, the aluminium may optionally be present in very small amounts, for example 0.1% to 5% by weight of the particulate metal, whilst still providing a coating of glossy appearance.

[0027] The particulate metal content of the coating composition will not exceed about 40% by weight of the total weight of the composition to maintain the best coating appearance and will be at least 10% by weight to achieve a glossy coating appearance.

[0028] The metal may be formulated or pasted in one or more solvents in minor amounts, for example dipropylene glycol and / or white spirit, especially when the metal has been prepared in lamellar form. The solvent-containing particulate metals are usually used in the form of pastes, which may be used directly with other ingredients of the composition. However, the particulate metals may also be used in a dry form in the coating composition.

[0029] The silane advantageously comprises a silane carrying at least one function hydrolyzable into a hydroxyl function chosen from a C1-C4, preferably C1-C2, alkoxy radical. The silane advantageously carries three functions hydrolyzable into a hydroxyl function, preferably identical.

[0030] The silane may also carry an epoxy function (oxirane), which promotes crosslinking and adhesion to the substrate. The term "functionality hydrolyzable into a hydroxyl function" means any chemical function capable of reacting with water to transform into a hydroxyl-OH function.

[0031] The silanes in the monomer mixtures of the present invention serve as binding agents and improve the adhesion of the coating and its resistance to corrosion.

[0032] The silane is part of the mixture of monomers present between 2% and 50% in the composition according to the invention and advantageously represents between 40 and 70%, preferably between 40 and 60%, more preferably between 50 and 60% by weight of the total weight of said mixture of monomers.

[0033] The silane is advantageously easily dispersed in the aqueous medium and is preferably soluble after hydrolysis in such a medium. The silane used is advantageously an epoxy-functional silane chosen from epoxy-functional di- or trimethoxysilane and epoxy-functional di- or triethoxysilane, as well as mixtures thereof, in particular gamma-glycidoxypropyltrimethoxysilane, beta-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidyloxypropyltriethoxysilane or 4-(trimethoxy silyl)butane-1,2-epoxide.

[0034] The liquid medium of the coating composition is practically always water or a combination of water and organic solvent. Other solvents may optionally be used but preferably only in very small amounts. Typically, the composition comprises 28 to 65% by weight of water, based on the total weight of the composition.

[0035] According to an advantageous variant of the invention, the coating composition further comprises 1 to 7%, preferably 1 to 5%, by weight of organic solvent or a mixture of organic solvents, relative to the total weight of the composition. The quantity of VOCs released and especially of degradation products is therefore very limited.

[0036] The organic solvents are advantageously chosen from the group consisting of glycolic solvents such as glycol ethers, in particular diethylene glycol, triethylene glycol and dipropylene glycol, acetates, propylene glycol, polypropylene glycol, nitropropane, alcohols, ketones, propylene glycol methyl ether, 2,2,4-trimethylpentanediol (1,3) isobutyrate (texanol), white spirit and mixtures thereof. Dipropylene glycol is particularly advantageous, in particular for economic and environmental reasons.

[0037] When the metal particles have been prepared in lamellar form in a solvent, the resulting particulate metal may be in the form of a paste. It may then constitute a part of the organic solvent of the composition according to the invention.

[0038] According to an advantageous variant, the coating composition further comprises one or more corrosion-inhibiting pigments such as aluminum tri or polyphosphate, phosphates, molybdates, zinc, strontium, calcium, barium, zirconium silicates and mixtures thereof, at levels of the order of 0.2 to 4% by weight, relative to the total weight of the coating composition.

[0039] The coating composition according to the invention may further comprise a thickening agent. The thickening agent is advantageously chosen from the group consisting of cellulose derivatives such as hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, cellulose acetate butyrate, xanthan gum, associative thickeners of polyurethane or acrylic type, silicas, silicates such as optionally treated magnesium and / or lithium silicates or organophilic clays and mixtures thereof. The thickening agent content is advantageously less than 7% by weight relative to the total weight of the composition, advantageously between 0.005 and 7% by weight relative to the total weight of the composition.

[0040] The coating composition according to the invention may also comprise one or more wetting agents, in a content advantageously less than 4% by weight, advantageously between 0.1 and 4% by weight, relative to the total weight of the composition. The wetting agents are advantageously chosen from C11 to C20 fatty alcohol alcoholates, such as fatty alcohol methoxylates, fatty alcohol ethoxylates and fatty alcohol propoxylates, as well as from C8 to C12 alkylated glycosides, such as D-pentose alkyl, D-glucose alkyl and polyglycoside alkyls.

[0041] The coating composition according to the invention may also comprise one or more antifoaming agents, in a content advantageously less than 4% by weight, advantageously between 0.05 and 4% by weight, relative to the total weight of the composition. The antifoaming agents are advantageously chosen from compounds of the polysiloxane or polyether siloxane family.

[0042] The coating composition according to the invention may also comprise one or more pH regulators, in a content advantageously less than 4% by weight, advantageously between 0.05 and 4% by weight, relative to the total weight of the composition. The pH regulator is advantageously chosen from oxides and hydroxides of alkali metals, advantageously lithium and sodium, as well as oxides and hydroxides of metals belonging to groups IIA and IIB of the periodic table, such as compounds of calcium, barium, magnesium and zinc. The pH regulator may also be a precious metal carbonate or nitrate. The pH regulator may also be chosen from amines such as triethylamine, methyldiethylamine, methyldiethanolamine and dimethylethylamine.

[0043] The coating composition according to the invention may also comprise one or more passivating agents, in a content advantageously less than 4% by weight, between 0.1 and 4% by weight, relative to the total weight of the composition.

[0044] The composition according to the invention may also comprise phosphates, phosphorus-containing substituents, such as aluminum triphosphate and ferrophosphate (pigment), inorganic salts, in amounts of less than 3% by weight relative to the weight of the composition.

[0045] The present invention also relates to the method of manufacturing said coating composition. The manufacturing method comprises the following steps: (a) preparing a binder by introducing silane, organic silicate and titanate into an aqueous solution; (b) the reduction of the rate of alcohols generated by an evaporation process with compensation by the addition of water; and (c) adding the metal particles and additives to the composition obtained in step (b).

[0046] In another embodiment, the manufacturing method comprises the following steps: (a) preparing a binder by introducing silane, organic silicate and titanate into an aqueous solution; (b) preparing a solvent-based composition containing the metal particles and the additives; then (c) adding and solubilizing the composition obtained in step (a) in the composition obtained in step (b).

[0047] The present invention also relates to the coating obtained by applying the coating composition according to the invention to a substrate, advantageously by spraying, dipping-draining or dipping-centrifuging, the coating layer then being subjected to a baking operation preferably carried out at a temperature of between 180°C and 250°C, preferably 180°C and 220°C, for approximately 10 to 60 minutes, by supplying thermal energy, such as by convection or infrared, or for approximately 30 seconds to 5 minutes by induction.

[0048] According to an advantageous embodiment, the anti-corrosion coating will result from an application operation involving, prior to a baking operation, a drying operation of the coated metal parts, by supplying thermal energy, such as by convection, infrared or induction, at a temperature between 30 and 250°C, advantageously of the order of 70°C, by convection or infrared for 10 to 30 minutes on line or for approximately 30 seconds to 5 minutes by induction. Before coating, it is advisable in most cases to remove foreign matter from the surface of the substrate, in particular by careful cleaning and degreasing.

[0049] Under these conditions, the thickness of the dry coating film thus applied is between 3 qm (approximately 11 g / m2) and 30 qm (approximately 110 g / m2) and preferably between 4 qm (approximately 15 g / m2) and 12 qm (approximately 45 g / m2), more particularly between 5 qm (approximately 18 g / m2) and 10 qm (approximately 40 g / m2).

[0050] The present invention also extends to the metallic substrate, preferably made of steel or steel coated with zinc or a zinc-based layer deposited by different application methods including mechanical deposition, cast iron and aluminum, provided with an anti-corrosion coating according to the invention applied using the aforementioned compositions.

[0051] The metal substrate may be pretreated, for example by chromate or phosphate treatment. Thus, the substrate may be pretreated to have, for example for example, an iron phosphate coating in an amount of 0.1 to 1 g / m2 or a zinc phosphate coating in an amount of 1.5 to 4 g / m2.

[0052] The present invention also relates to the use of the composition according to the invention as an anti-corrosion coating for metal parts.

[0053] The present invention also relates to an aqueous composition of a mixture of monomers comprising silane, at least one silicate and at least one titanate, intended for the preparation of a coating composition according to the present invention for a metal substrate in aqueous dispersion, comprising (percentages by weight): - Between 0 and 7%, more preferably between 0 and 5% of a water-soluble organic solvent; - Between 40 and 70%, preferably between 40 and 60%, more preferably between 50 and 60% by weight of silane; - Between 10 and 40%, preferably between 15 and 30%, more preferably between 20 and 30% by weight of at least one silicate; and - Between 10 and 40%, preferably between 15 and 30%, more preferably between 15 and 25% by weight of at least one titanate; - Water: qsp 100%. Description of figures

[0054] [Fig.l]: Anti-corrosion performance of coatings currently on the market. AS IS (As Is) = part directly subjected to the salt spray (BS) resistance test according to ISO 9227; CTV = mechanical damage by 5 drops from 1 m high + 5 minutes of vibrating bowl at approximately 100 Hz before BS test; CTH = thermal shock of 96 hours at 180°C before BS test. Note @5 = BS time without observation of red rust. Note @4.8 = BS time with a red rust rate between 0.1 and 5%, for one sample out of 5 samples put to BS.

[0055] [Fig.2]: Anti-corrosion performance of anti-corrosion coating compositions according to the invention. AS IS (As Is) = part subjected directly to the salt spray resistance test (BS) according to ISO 9227; CTV = mechanical damage by 5 drops from 1 m high + 5 minutes of vibrating bowl before BS test; CTH = thermal shock of 96 hours at 180°C before BS test. ACT: Anticorrosive cyclic test according to the VOLVO manufacturer standard “STD 423-0014”. Note @5 = BS time without observation of red rust. Note @4.8 = BS time with a red rust rate between 0.1 and 5%, for one sample out of 5 samples put to BS.

[0056] Examples

[0057] Example 1: Performance of the composition according to the invention

[0058] The formulations of zinc flake anti-corrosion coating composition for metal parts currently on the market, such as Geomet®, have very good anti-corrosion performances even after mechanical damage and thermal shock of 4 days at 180°C (resistance to salt spray according to ISO 9227 - BS»720hrs) with a curing carried out at 310°C but lower performances with a curing less than or equal to 220°C (see [Fig.l]). The inventors concluded that the lower performances of these formulations following a curing at 220°C were linked to their chemical composition, mainly to the composition of the binder which composes them. In addition, these formulations can have a high VOC level.

[0059]

[0060] The formulas currently on the market can be summarized as follows in terms of the quantity of raw materials introduced: ABC Silane 9.9 13.8 12.2 Titanate 3.8 4.3 4.3 Silicate (TEOS) 0.0 0.7 0.9 Additives 4.7 5.0 4.8 Corrosion inhibitors 1.7 1.9 1.9 Water 40.9 46.4 36.8 Solvents 13.5 2.3 14.3 Zinc 22.4 23.9 21.8 Aluminum 3.2 1.6 3.0

[0061] The composition according to the invention is a selection of raw materials with very few VOCs and a specific selection of monomers leading via polycondensation to the formation of the sol-gel network. This sol-gel network surprisingly makes it possible to obtain a sufficient crosslinking density at low temperature (220°C) in order to have an efficient percolation of the lamellar zinc particles in the film and thus promote the circulation of electrons in the coating. In the event of over-crosslinking, the removal of the binder could very significantly reduce the barrier effect of the film by allowing the electrolyte to penetrate too quickly, not leaving time for the corrosion mechanisms including the sacrificial effect of zinc to take place.

[0062] The monomers used to synthesize the sol-gel binder of the present examples are 3-glycidyloxypropyltriethoxysilane, TEOS and tetraethoxytitanate (TET), in the following proportions:

[0063] [Tables2] Example 1 Example 2 Example 3 Silane 12.4 12.4 12.4 Titanate 5 5 5 Silicate (TEOS) 4.1 4.1 4.1 Additives 3.7 3.7 3.7 Corrosion inhibitors 1.5 1.5 1.5 Water 46.7 46.7 46.7 Solvents 0 0 0 Zinc 26.7 26.17 25.37 Aluminum 0 0.53 1.33

[0064] As illustrated in [Fig.2], the examples of compositions according to the invention give better anti-corrosion performances than those existing with a cooking temperature of only 220°C.

[0065] The results show good performance on screws with a layer weight of 27-33 g / m2 after application, but also after mechanical damage. A thermal shock of 4 days at 180°C reduces the performance level while still remaining at ~800h of resistance.

[0066] This loss of performance in salt spray after mechanical and thermal shocks is not found in the ACT cyclic test (Anticorrosive cyclic test according to the VOLVO manufacturer standard “STD 423-0014”): an increase of +100% in performance can be visible between an AS IS and CTV+CTH system.

[0067] Additives such as metallic aluminum can also have a positive impact on salt spray performance.

[0068] As shown in [Fig.2], the incorporation of metallic aluminum (examples 2 and 3) made it possible to increase the anti-corrosion properties (BS), in particular after thermal shock, without major impact on the viscosity of the products, and also made it possible to regulate the activity of the zinc upstream, these observations could be verified in particular using electrochemistry (potentiodynamics).

Claims

Claims

1. Anti-corrosion coating composition for metal parts based on a particulate metal in aqueous dispersion comprising in the following proportions (percentages by weight): - Between 2 and 50% of a mixture of monomers comprising silane, at least one silicate and at least one organic titanate; - Between 10 and 40% of at least one particulate metal or a mixture of particulate metals; - water: qsp 100%; characterized in that said mixture of monomers comprises in the following proportions (percentages by weight): - Between 40 and 70%, preferably between 40 and 60%, more preferably between 50 and 60% by weight of silane; - Between 10 and 40%, preferably between 15 and 30%, more preferably between 20 and 30% by weight by weight of at least one silicate; and - Between 10 and 40%, preferably between 15 and 30%, more preferably between 15 and 25% by weight of at least one titanate.

2. Composition according to claim 1, characterized in that the at least one silicate is an organic silicate of formula Si(OR)4 in which R1, R2, R3 and R4 independently represent an optionally substituted C1-C8 alkyl radical, preferably tetraethyl orthosilicate (TEOS) of formula Si(OEt)4.

3. Composition according to any one of claims 1 or 2, characterized in that the particulate metal is chosen from zinc and aluminum, as well as their alloys and their mixtures or their alloys with manganese, magnesium, tin or silicon.

4. Composition according to any one of claims 1 to 3, characterized in that the silane comprises a silane carrying at least one function which can be hydrolyzed into a hydroxyl function chosen from a C1-C4 alkoxy radical.

5. Composition according to any one of claims 1 to 4, characterized in that the silane is chosen from a di- or trimethoxysilane having an epoxy function or a di- or triethoxysilane having an epoxy function, as well as their mixtures, in particular gamma-glycidoxypropyltrimethoxysilane, beta- (3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidyloxypropyl triethoxysilane or 4-(trimethoxysilyl)butane-1,2-epoxide.

6. Composition according to any one of claims 1 to 5, characterized in that the titanate is chosen from tetraethoxytitanate, tetraisopropoxytitanate, tetrabutoxytitanate, preferably tetraethoxytitanate (TET).

7. Composition according to any one of claims 1 to 6, characterized in that it further comprises from 1 to 7%, preferably between 1 and 5%, by weight of an organic solvent or a mixture of organic solvents, relative to the total weight of the composition.

8. Anticorrosive coating of metal parts, characterized in that it is obtained from a coating composition according to any one of claims 1 to 7, by spraying, dipping-draining or dipping-centrifuging, the coating layer then being subjected to a baking step by supplying thermal energy, such as by convection, infrared or induction, preferably carried out at a temperature between 180°C and 250°C, preferably between 180°C and 220°C, for approximately 10 to 60 minutes by convection or infrared, or for 30 seconds to 5 minutes by induction.

9. Use of the composition according to any one of claims 1 to 7 as an anti-corrosion coating for metal parts.

10. An aqueous composition of a mixture of monomers comprising silane, at least one silicate and at least one titanate, intended for the preparation of a coating composition according to any one of claims 1 to 7 for a metal substrate in aqueous dispersion, comprising in the following proportions (percentages by weight): - Between 0 and 7%, more preferably between 0 and 5% of a water-soluble organic solvent; - Between 40 and 70%, preferably between 40 and 60%, more preferably between 50 and 60% by weight of silane; - Between 10 and 40%, preferably between 15 and 30%, more preferably between 20 and 30% by weight of at least one silicate; and - Between 10 and 40%, preferably between 15 and 30%, more preferably between 15 and 25% by weight of at least one titanate; - Water: qsp 100%.

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