JP2014528520A - Method for anticorrosion treatment of solid metal substrate and treated solid metal substrate obtainable by such method - Google Patents

Abstract

The present invention applies a solution referred to as a treatment solution comprising at least one alkoxysilane and at least one cerium (Ce) cation in an aqueous alcohol liquid composition on an oxidizable surface of a solid metal substrate. The treatment solution is suitable for forming a mixed matrix by hydrolysis / condensation of each alkoxysilane (s) and each cerium (Ce) cation on the surface of the solid metal substrate. , An anticorrosion treatment method wherein the molar ratio (Si / Ce) of the silicon element of the alkoxysilane (s) to the cerium (Ce) cation (s) is 50 to 500, the cerium (Ce) cation (singular) Or a plurality of) exhibit a concentration of 0.005 mol / L to 0.015 mol / L in the treatment solution To.

Description

  The present invention relates to an anticorrosion treatment method for a solid metal substrate, particularly a substrate made of aluminum or aluminum alloy. The invention further relates to a solid metal substrate treated against corrosion, obtainable by such a method.

  Such anticorrosion treatment methods have applications in the general field of surface treatment of solid metal substrates, particularly metal parts. Such a method finds application in the field of transportation, in particular in the fields of ships, automobiles and aircraft, where the corrosion protection of metal parts is a problem.

  Methods for surface treatment of solid metal substrates using chromium-based reactants are already known. Such reactants are harmful to the environment and human health and their use is regulated.

  In order to avoid the disadvantages associated with the use of chromium, it has been proposed to form a silica gel based coating on the surface of an aluminum alloy substrate by the sol-gel method (Pepet et al., 2004, Journal of). Non-Crystalline Solids, 348, 162-171). Such treatment is performed by immersing and removing the aluminum alloy substrate in a mixed solution of tetraethyl orthosilicate (TEOS) and methyltriethoxysilane (MTES) containing cerium nitrate ("dip coating"). With such a method it is not possible to obtain an anticorrosion coating which simultaneously exhibits improved mechanical strength properties, in particular peel resistance, and also improved self-healing properties and barrier effects.

  The present invention provides the above-mentioned disadvantages by proposing an anticorrosion treatment method for solid metal substrates that does not require the use of chromium derivatives, in particular, carcinogenic, mutagenic and reproductive toxic chromium (VI) derivatives. The purpose is to avoid.

  Further, from “Zhong et al, (2010), Progress in Organic Coatings, 69, 52-56”, an aqueous alcohol solution of γ-glycidoxypropyltrimethoxysilane (GPTMS) and vinyltriethoxysilane (VETO) was prepared. There is known a method of treating an aluminum alloy that is prepared, then hydrolyzed / condensed the aqueous alcohol solution to form a gel, and then added an amount of cerium nitrate to the formed gel.

Pepe et al. , 2004, Journal of Non-Crystalline Solids, 348, 162-171. Zhong et al, (2010), Progress in Organic Coatings, 69, 52-56. Landau L. D. and Levic B. G. (1942), Acta Physiochim. URSS, 77, 42-54 Yoldas (Yoldas BE et al, (1975), J. Mater. Sri., 10, 1856) Yoldas B.M. E. (J. Mater. Sri., (1975), 10, 1856). Daniel H. , Et al (2007), Nano Lett. , 7; 11, 3489-3492

  An object of the present invention is to propose an anticorrosion treatment method suitable for forming an anticorrosion coating with high mechanical strength on the surface of a solid metal substrate.

  The present invention also provides such an anti-corrosion treatment method which makes it possible to obtain an anti-corrosion coating layer with controlled thickness, in particular with a thickness of 1 μm to 15 μm, which meets industrial recommendations, in particular industrial recommendations in the field of aircraft. The purpose is to propose.

  Another object of the present invention is a method for anticorrosion treatment of a solid metal substrate, particularly an aircraft metal part, wherein the thickness on the solid metal substrate is substantially uniform, has a covering property, and is flat. The present invention proposes a method suitable for enabling the formation of an anticorrosive coating on the solid metal substrate having a oxidative property. Planarity means that such a coating exhibits a substantially flat free outer surface, i.e., an outer surface opposite the substrate, regardless of the presence of structural defects on the underlying solid metal substrate surface. Means. In particular, it is an object of the present invention to propose such a method which is suitable for enabling the formation of an anticorrosion coating which does not crack at the structural defect.

  The present invention is also directed to such a method suitable for enabling the formation of a corrosion protection layer resistant to cracking.

  The present invention further provides such a method suitable for enabling the formation of a protective coating on the surface of a solid metal substrate, wherein the protective coating is a passive protective property of said substrate against corrosive external environments, in particular a barrier. The aim is to simultaneously show passive protective properties by effect and active protective properties by limiting the progression of corrosion at sites of accidental pinholes that may affect self-healing and anticorrosion coatings.

  The present invention is also directed to such an anticorrosion treatment method suitable for being applied on a polished solid metal substrate or an unpolished solid metal substrate.

  The present invention further aims to achieve all these objectives at low cost by proposing a method that is simple and requires only a step of contacting the solid metal substrate with the solution for its implementation.

  The present invention further and more specifically aims to propose such a method that meets the constraints on safety and environmental considerations.

  The present invention additionally aims at proposing such a solution that protects the work habits of the staff, ie is simple to use and involves only a few operations in its execution.

  The present invention is also directed to such an anticorrosion treatment method using a treatment solution having a simple composition compared to prior art treatment solutions.

  Accordingly, the present invention is also directed to an anti-corrosion coating that exhibits improved protective properties, particularly improved anti-corrosion properties over time, as compared to prior art anti-corrosion coatings.

For this purpose, the present invention relates to an oxidizable surface of a solid metal substrate, in an aqueous alcohol liquid composition, at least one alkoxysilane, and
At least one cerium (Ce) cation,
A solution called a treatment solution is applied, and the treatment solution forms a mixed matrix on the surface of the solid metal substrate by hydrolysis / condensation of each alkoxysilane (s) and each cerium (Ce) cation. Suitable to get and
The treatment solution is an anticorrosion treatment method in which the molar ratio (Si / Ce) of silicon element of alkoxysilane (s) to cerium (Ce) cation (s) is 50 to 500, particularly 80 to 250. ,
Cerium (Ce) cation (s) are present in the treatment solution in the range of 0.005 mol / L to 0.015 mol / L, in particular 0.005 mol / L to 0.01 mol / L, preferably about 0. The present invention relates to a method characterized by exhibiting a concentration of 010 mol / L.

  In the process according to the invention, hydrolysis / condensation of at least one alkoxysilane and at least one cerium (Ce) cation in an aqueous alcohol solution with said at least one alkoxysilane and said at least one cerium (Ce) cation. To form a mixed matrix by hydrolysis / condensation of each alkoxysilane (s) and each cerium (Ce) cation on the surface of the solid metal substrate. And applying the treatment solution to the oxidizable surface of the solid metal substrate.

  In the method of the present invention, hydrolysis / condensation of each alkoxysilane (s) is carried out in the treatment solution in the presence of each cerium (Ce) cation (s), the treatment solution being The silicon element molar ratio (Si / Ce) of the starting alkoxysilane (s) to the cerium (Ce) cation (s) is from 50 to 500, in particular from 80 to 250.

  We have chosen a concentration value for the cerium cation in the treatment solution, not a random choice of concentration, but conversely, this selection is completely unpredictable and has surprising results not described in the prior art, According to the results, the selected concentration of the cerium (Ce) cation in the anti-corrosion treatment solution of the solid metal substrate (1) obtains optimum adhesion of the treatment solution to the surface of the solid metal substrate, (2) Formation of a mixed matrix of passive protection of the solid metal substrate, in particular by a barrier effect suitable for limiting the formation of corrosion products of the solid metal substrate exhibiting pinhole scratches, and (3 ) Improved physical resistance to mechanical stress, especially exfoliation resistance, crack resistance, and plastic deformation properties, and corrosion resistance (by immersion in a corrosive solution of 0.05 mol / L NaCl in water, 1 Day, Day and corrosion treatment for about 14 days) forms a protective mixing matrix according illustrating a, but noticed that is possible at the same time.

  Such physical resistance to mechanical stresses is in particular determined by techniques known per se to the person skilled in the art, in particular for the evaluation of nanoindentation-Young's modulus and hardness (eg Vickers nanohardness) or for solid metal substrates It is evaluated by continuous load scratch (“nano scratch”) for the evaluation of anticorrosion coating adhesion and peel resistance on the material surface.

  Advantageously, the cerium cation is a single cerium cation, and the concentration of the single cerium cation in the treatment solution is from 0.005 mol / L to 0.015 mol / L, in particular from 0.005 mol / L to 0.01 mol / L, preferably about 0.01 mol / L.

  Advantageously, the cerium cation is a composition comprising a plurality of different cerium cations, and the cumulative concentration of the plurality of different cerium cations in the treatment solution is also from 0.005 mol / L to 0.015 mol / L, in particular from 0. 005 mol / L to 0.01 mol / L, preferably about 0.01 mol / L.

The anticorrosion coating of the present invention, ie a coating obtained with a treatment solution containing a concentration of 0.005 mol / L to 0.015 mol / L of cerium cation, in particular Ce ^III , is:
The critical value (Hv) of elastic deformation measured by nanoindentation, which is maximum at a cerium concentration of 0.01 mol / L in the treatment solution and about 39,
The critical load value F _D (mN) of the peeling of the anticorrosion coating on the solid metal substrate, which is maximum at a cerium concentration of 0.01 mol / L in the treatment solution and about 24 mN,
The crack initiation critical load value F _f (mN) of the anticorrosion coating, which is maximum at a cerium concentration of 0.01 mol / L in the treatment solution and about 15 mN;
The maximum value F _DP (mN) of crack-free elastic deformation critical load of about 6 mN at a cerium concentration of 0.01 mol / L in the treatment solution,
Indicates.

We have found that, according to the present invention, a cerium cation concentration of 0.005 mol / L to 0.015 mol / L in the treatment solution is applied to the anticorrosive coating on the solid metal substrate, and after deposition into the corrosive solution. It has been found that it provides optimum resistance to corrosion prior to immersion. On the other hand, a cerium cation concentration of more than 0.015 mol / L in the treatment solution results in significant degradation of the barrier effect of the protective layer and reduced resistance to corrosion prior to immersion in the corrosive solution. The surface resistance in the corrosive medium of such a protective layer of 6.3 μm obtained by anticorrosion treatment of a solid metal substrate with a treatment solution containing 0.05 mol / L cerium cation is corrosive to the metal substrate. It is about 2.8 · 10 ⁶ Ω · cm ² immediately after being immersed in the medium. The surface resistance in a corrosive medium of such a protective layer of 6.3 μm, obtained by anticorrosion treatment of a solid metal substrate with a treatment solution containing 0.1 mol / L cerium cation, is measured by electrochemical impedance spectroscopy (EIS). ), It is about 2.1 · 10 ⁵ Ω · cm ² immediately after the metal substrate is immersed in a corrosive medium.

Furthermore, the cerium cation concentration of 0.005 mol / L to 0.015 mol / L in the treatment solution according to the present invention enables the following:
-Reduction of the contact angle of the treatment solution to the solid metal substrate, which is an indication of improved wettability to the treatment solution on the surface of the solid metal substrate and improved application of the treatment solution onto the surface of the solid metal substrate. ,
-Improved fixability of the mixed matrix obtained from the treatment solution onto the surface of the solid metal substrate,
-Improved mass increase of the treatment solution at the surface of the solid metal substrate. Such a mass increase reveals the structuring effect of the treatment solution and the mixed matrix obtained from the treatment solution. and,
-Ce ^IV is changed to Ce ^III in the treatment solution and in the mixed sol. The Ce ^III / Ce ^IV distribution is measured by surface X-ray photoelectron spectroscopy (XPS).

  The inventors have found that such cerium cation concentrations of 0.005 mol / L to 0.015 mol / L in the treatment solution according to the present invention provide the mixed matrix with passive protective properties due to the barrier effect on the solid metal substrate. While maintaining at least the mechanical properties of the mixed matrix obtained from the treatment solution, the treatment solution has improved rheological performance and solid metal substrate surface compared to treatment solutions that do not exhibit such concentrations. It has been found that it is suitable for imparting close adhesion performance.

According to the invention, advantageously each alkoxysilane is:
The following general formula (I)
Si (O—R ₁ ) ₄ (I)
(Where:
Si is a silicon element, O is an oxygen atom,
R ₁ is:
( ₁ ) A hydrocarbon group represented by the formula [—C _n H _{2n + 1} ] (wherein n is an integer of 1 or more), particularly methyl, ethyl,
■ 2-hydroxyethyl group _{(HO-CH 2 -CH 2 -} ), and ■ the general formula 'acyl group (wherein represented by _1, R' -CO-R ₁ in the formula _{[-C n H 2n + 1]} A hydrocarbon group represented (n is an integer of 1 or more), particularly methyl or ethyl)
Selected from the group consisting of
Tetraalkoxysilane represented by:
The following general formula (II):
Si (O—R ₂ ) _4-a (R ₃ ) _a (II)
(Where:
R ₂ is:
( ₁ ) A hydrocarbon group represented by the formula [—C _n H _{2n + 1} ] (wherein n is an integer of 1 or more), particularly methyl, ethyl,
■ 2-hydroxyethyl group _{(HO-CH 2 -CH 2 -} ), and ■ the general formula 'acyl group (wherein represented by _1, R' -CO-R ₁ in the formula _{[-C n H 2n + 1]} A hydrocarbon group represented (n is an integer of 1 or more), particularly methyl or ethyl)
Selected from the group consisting of
R ₃ is an organic group bonded to the silicon element (Si) of alkoxysilane by a Si—C bond, particularly a carbon atom (s), a hydrogen atom (s), and a nitrogen atom (single) as required. Or an organic group formed by oxygen atom (s) and optionally sulfur atom (s) and phosphorus atom (s),
A is a natural number in the range] 0,4 [-preferably 1-)
It selects from the group which consists of alkoxysilane represented by these.

  Advantageously, in a first variant of the process of the invention, each alkoxysilane is replaced with tetraethoxysilane (TEOS), tetramethoxysilane (TMOS), tetraacetoxysilane (TAOS) and tetra-2-hydroxyethoxysilane ( The group is selected from the group consisting of THEOS).

Advantageously, in a second variant of the process according to the invention, the group R ₃ of each alkoxysilane has 1 to 10 carbon atoms in the methacrylate, acrylate, vinyl, alkyl group (s), Selected from the group consisting of epoxyalkyl and epoxyalkoxyalkyl selected from linear alkyl groups, branched alkyl groups and cyclic alkyl groups.

Advantageously, the group R ₃ of each alkoxysilane is selected from the group consisting of 3,4-epoxycyclohexylethyl and glycidoxypropyl.

  Advantageously, each alkoxysilane is glycidoxypropyltrimethoxysilane (GPTMS), glycidoxypropylmethyldimethoxysilane (MDMS), glycidoxypropylmethyldiethoxysilane (MDES), glycidoxypropyltriethoxysilane ( GPTS), methyltriethoxysilane (MTES), dimethyldiethoxysilane (DMDES), methacryloxypropyltrimethoxysilane (MAP), 3- (trimethoxysilyl) propylamine (APTMS), 2- (3,4-epoxy) Cyclohexyl) ethyl-triethoxysilane (ECHETES), 2- (3,4-epoxycyclohexyl) ethyl-trimethoxysilane (ECHETMS) and 5,6-epoxyhexyltriethoxysilane (EHTES) It is selected from the group consisting of.

  In this second variant of the method of the invention, a mixed organic / inorganic matrix is formed by hydrolytic condensation of each alkoxysilane.

  According to the invention, the treatment solution advantageously comprises a single alkoxysilane.

  According to the invention, the treatment solution advantageously comprises at least one metal alkoxide.

According to the invention, each metal alkoxide is advantageously represented by the following general formula (VII):
M ′ (O—R ₉ ) _{n ″} (VII)
(Where:
M ′ is a metal element selected from the group consisting of aluminum (Al), vanadium (V), titanium (Ti) and zirconium (Zr),
R ₉ is an aliphatic hydrocarbon group represented by the formula [—C _n H _{2n + 1} ] (n is an integer of 1 or more) (especially methyl, ethyl, propyl, butyl, especially the formula [CH ₃ —CH ₂ a _(CH 3) CH-] is selected from the group consisting of sec-butyl represented by), -
N ″ is a natural number representing the valence of the metal element M ′).

  In the process according to the invention, the hydrolysis of each alkoxysilane and each metal alkoxide forms a reactive species that can be dispersed in a uniform manner in the treatment solution and polymerized to form a mixed organic / inorganic matrix. Thus, an organic / inorganic mixed matrix is formed by hydrolytic condensation of each alkoxysilane and each metal alkoxide.

  Advantageously, each metal alkoxide is an aluminum alkoxide, in particular aluminum tri (s-butoxide), aluminum tri (n-butoxide), aluminum tri (ethoxide), aluminum tri (ethoxyethoxyethoxide) and aluminum tri (isopropoxide). ), Titanium alkoxide (especially titanium tetra (n-butoxide), titanium tetra (isobutoxide), titanium tetra (isopropoxide), titanium tetra (methoxide) and titanium tetra (ethoxide)), vanadium alkoxide, (especially vanadium Tri (isobutoxide) oxide and vanadium tri (isopropoxide) oxide), and zirconium alkoxide (especially zirconium tetra (ethoxide), zirconium tetra (ii) Propoxide), zirconium tetra (n- propoxide), selected from the group consisting of zirconium tetra (n- butoxide) and zirconium tetra (t-butoxide)).

Advantageously, each metal alkoxide is an aluminum alkoxide represented by the following general formula (III):
Al (OR ₄ ) _n (III)
(Where:
Al and O are aluminum element and oxygen element, respectively
R ₄ is an aliphatic hydrocarbon group having 1 to 10 carbon atoms (particularly methyl, ethyl, propyl, butyl, especially a group represented by the formula [CH ₃ —CH ₂ (CH ₃ ) —CH—]). Selected from the group consisting of dibutyl),
N is a natural number representing the valence of the aluminum element (Al).

  According to the invention, the treatment solution advantageously comprises a single metal alkoxide. Thus, an inorganic mixed matrix is formed by hydrolytic condensation of each alkoxysilane and a single metal alkoxide. Advantageously, the treatment solution comprises a single metal alkoxide and a single alkoxysilane. Thus, an inorganic mixed matrix is formed by hydrolytic condensation of a single alkoxysilane and a single metal alkoxide.

  Advantageously, the treatment solution comprises a single aluminum alkoxide as the single metal alkoxide.

  Thus, a treatment solution comprising a single metal alkoxide (especially aluminum alkoxide) and a single alkoxysilane is formed, which treatment solution is very simple in composition and yet provides a high performance anticorrosion coating. Suitable for

  Advantageously, the single aluminum alkoxide comprises the group consisting of aluminum tri (s-butoxide), aluminum tri (n-butoxide), aluminum tri (ethoxide), aluminum tri (ethoxyethoxyethoxide) and aluminum tri (isopropoxide). Selected from.

  Advantageously, the molar ratio of alkoxysilane to metal alkoxide in the treatment solution is 99/1 to 50/50. Advantageously, the molar ratio of total alkoxysilane to total metal alkoxide in the treatment solution is 99/1 to 50/50.

  According to the invention, the molar ratio of alkoxysilane to metal alkoxide (especially aluminum alkoxide) in the treatment solution is preferably from 85/15 to 6/4, in particular from 8/2 to 64/36. Advantageously, the molar ratio of total alkoxysilane to total metal alkoxide in the treatment solution is 8/2 to 6/4.

  According to the invention, the solid metal substrate is advantageously from the group consisting of oxidizable materials, in particular aluminum (eg 2024T3 alloy), titanium (eg TA6V alloy), magnesium (eg AZ30 alloy) and alloys thereof. It is made of a selected material.

  According to the invention, the treatment solution is advantageously applied by dipping / removing a solid metal substrate into the treatment solution.

  Advantageously, the removal of the solid metal substrate from the treatment solution takes place at a predetermined speed of 5 cm / min to 10 cm / min.

  According to the invention, the treatment solution is advantageously applied by atmospheric spraying on the surface of the solid metal substrate.

  The inventors have realized that the thickness of the mixing matrix can be controlled by the removal rate of the solid metal substrate from the processing solution. In accordance with the Landau-Levic law (Landau LD and Levic BG, (1942), Acta Physiochim. URSS, 77, 42-54), the thickness of the anticorrosive mixing matrix is determined for a treatment solution of known viscosity. It is possible to vary from a value of 1 μm for a picking speed of 1 cm / min to a value of 14 μm for a picking speed of 20 cm / min. In particular, it is possible to obtain a mixed matrix with a thickness of 5 μm with a removal speed of 7 cm / min.

  The thickness of the mixing matrix is determined by methods known per se to the person skilled in the art, in particular by interference profilometry or by measuring the induced Foucault current.

  Advantageously, the treatment solution further comprises a plasticizer selected from the group consisting of PEG.

Advantageously, the treatment solution contains a dye. Such a dye is selected from the group consisting of rhodamine B (CAS 81-88-9), malachite green (“Brilliant Green”, CAS 633-03-4) and xylene cyanol (CAS 2850-17-1). Advantageously, a concentration of the processing solution of ^{5-10 -4} mol / L~10 ^-3 mol / L of rhodamine B, treatment of the malachite green ^{5-10 -4} mol / L~10 ^-3 mol / L Xylene cyanol is used at a concentration in the solution and at a concentration in the treatment solution of 5 · 10 ⁻⁴ mol / L to 10 ⁻³ mol / L.

  Advantageously, in the anticorrosion method according to the invention, the treatment solution is a nanoparticle formed of a colloidal dispersion of boehmite in the treatment solution, i.e. forms a colloidal dispersion of boehmite nanoparticles in the treatment solution. It contains boehmite solid nanoparticles represented by [—AlO (OH) —] at a certain loading.

  In the anticorrosion treatment method according to the present invention, in order to prepare a treatment solution, each alkoxysilane, each aluminum alkoxide, and if necessary, each metal alkoxide is converted from alcohol (especially ethanol, 1-propanol, and 2-propanol). And then adding an amount of water or, if necessary, an amount of an aqueous solution containing at least a lanthanoid cation and / or colloidal boehmite to form an anti-corrosion treatment solution. .

  Advantageously, the alcohol solution comprises at least the alkoxysilane (s) and the metal alkoxide (s) and an amount of water, or optionally lanthanoid cations and / or colloidal boehmite nanoparticles. An amount of aqueous solution is added to significantly preserve the rheological and thixotropic properties of the treatment solution.

  Advantageously, in a third variant of the anticorrosion treatment method according to the invention, the surface distribution of lanthanide cations (especially cerium cations) and / or vanadate comprising boehmite nanoparticles of the general formula AlO (OH) Is formed. Such boehmite nanoparticles, referred to as physisorbed boehmite nanoparticles, are known per se to the person skilled in the art, in particular by Yoldas (Yoldas BE et al, (1975), J. Mater. Sri., 10, 1856). Obtained by a procedure adapted from the procedure described.

  In this third variant of the method according to the invention, the inventors have resisted corrosion of a solid metal substrate treated with a treatment solution that has been subjected to immersion in a corrosion bath of 0.05 mol / L NaCl. The improvement of sex was confirmed.

Advantageously, in a fourth variant of the anticorrosion treatment method according to the invention, a treatment solution is formed comprising boehmite nanoparticles represented by the following general formula (VIII), referred to as doped boehmite:
Al _1-x (X) _x O (OH) (VIII)
(Where:
-X is an element selected from the group consisting of trivalent lanthanoids (particularly trivalent cerium), referred to as doping elements,
-X is a relative number from 0.002 to 0.01).

Such doped boehmite nanoparticles are selected from the group consisting of a solution of at least one aluminum precursor in water (particularly Al (OC ₄ H ₉ ) ₃ ) and the doping elements nitrate, sulfate, acetate and chloride. And a solution of a doping element cation to be mixed.

  In this fourth variant of the method according to the invention, the inventors have resisted corrosion of a solid metal substrate treated with a treatment solution that has been subjected to immersion in a corrosion bath of 0.05 mol / L NaCl. The improvement of sex was confirmed.

  Advantageously, the physisorbed boehmite nanoparticles and the doped boehmite nanoparticles have one large dimension and two smaller dimensions that are perpendicular to each other and perpendicular to the large dimension, the large dimension being Less than 200 nm (especially less than 100 nm, especially less than 50 nm, preferably 5 nm to 20 nm), the two smaller dimensions being less than 10 nm, preferably about 3 nm.

  According to the invention, the treatment solution advantageously comprises hollow boehmite nanoparticles at a loading.

  According to the present invention, the application of the treatment solution is advantageously followed by a heat treatment of the metal substrate suitable to allow the formation of a mixed matrix and the evaporation of the solvent.

  Advantageously, in the method of the invention, prior to applying the treatment solution, the oxidizable surface of the solid metal substrate is immersed in a solution called a conversion solution formed of at least one corrosion inhibitor in water, The corrosion inhibitor is selected from the group consisting of lanthanoid cations, and is formed of a solid solution having a oxidizable surface of the solid metal substrate bonded with a conversion solution and at least one covalent bond to the oxidizable surface. Stay in contact for a period suitable to form a conversion layer extending over the surface.

  In the fifth variation of the anticorrosion treatment method of the present invention, first, a conversion layer is formed on the oxidizable surface of the solid metal substrate by bringing the oxidizable surface into contact with the conversion solution. The treatment with the conversion solution makes it possible to form a conversion layer on the surface of the solid metal substrate instead of the metal oxide layer of the solid metal substrate, and the conversion layer naturally forms on the surface of the solid metal substrate. Corresponding to anticorrosion treatment in that it shows increased resistance to corrosion (especially measured by electrochemical impedance spectroscopy (EIS)) compared to the resistance of the oxide layer to corrosion.

  In fact, we first form a conversion layer on the oxidizable surface of a solid metal substrate, and then at least one alkoxysilane, at a concentration of 0.005 mol / L to 0.015 mol / L. By applying the treatment solution comprising cerium cation and, if necessary, at least one metal alkoxide, the oxidizable surface of the solid metal substrate is applied to the oxidizable surface of the solid metal substrate for a predetermined period (especially a period exceeding 1 hour). It has been found that the resistance to corrosion of the oxidizable surface of a solid metal substrate can be increased even after immersion in a corrosion bath, in particular in an aqueous bath of 0.05 mol / L NaCl.

The inventors have found that a conversion layer in which the treatment of the oxidizable surface of a solid metal substrate with a conversion solution has increased resistance to corrosion compared to a metal oxide layer of a solid metal substrate that has not been treated with a conversion solution. I guess that will lead to the formation of. Such a conversion layer is increased compared to the surface resistance value Z ′ (ω) of the metal oxide layer naturally formed on the surface of the solid metal substrate, according to the display of the electrochemical impedance diagram called “Nyquist” display. It is characterized by a surface resistance value Z ′ (ω) (Ω · cm ² ). The impedance Z (ω) is measured in a constant potential mode around a floating potential with a sinusoidal disturbance. The amplitude of the sine wave disturbance is set to 10 mV so as to satisfy the linear condition. The sweep frequency at the time of impedance measurement is 65 kHz to 10 mHz, and 10 points for each digit.

  The present inventors have found that such a conversion layer is composed of a mixed oxide of a lanthanoid and a constituent metal on the oxidizable surface of a solid metal substrate by energy dispersive spectroscopy (“EDS, Energy Dispersive Spectroscopy”). Showed that.

  Advantageously, the conversion layer extending over the surface of the solid metal substrate exhibits an average thickness of 1 nm to 200 nm.

  The inventors have found that the surface of the surface exceeds the limit value of the surface resistance of the aluminum oxide layer naturally formed on the surface of the aluminum alloy piece by increasing the immersion period of the solid metal substrate in the conversion solution according to the present invention. I noticed that the resistance could be increased.

  In addition, the inventors have also found that such treatment with a convertible solution of the oxidizable surface of a solid metal substrate does not result in any detectable increase in substrate mass. Such a conversion layer does not correspond to the crystallization of the lanthanoid oxide / hydroxide on the surface of the solid metal substrate.

  In particular, the treatment of the oxidizable surface of the solid metal substrate with the conversion solution is due to the formation of multiple covalent bonds between the lanthanoid element (Ln), which is a corrosion inhibitor, and the metal element (M) of the solid metal substrate. Allowing the formation of a self-healing conversion layer with active protection on the surface of the solid metal substrate. By chemical analysis of the binding energy (especially by X-ray photoelectron spectroscopy (XPS)), the inventors have determined that this covalent bond is of the M-O-Ln-O-type, where M is the metal of the solid metal substrate. It represents an element, O is an oxygen atom, and Ln has been shown to represent a corrosion inhibitor selected from lanthanoids.

  In the process according to the invention, at least one alkoxysilane (especially an alkoxysilane having an organic group), 0.005 mol / wt, on the oxidizable surface of the solid metal substrate and optionally on the surface of the conversion layer. L-0.015 mol / L concentration of cerium cation, and optionally hydrolysis of at least one metal alkoxide, alkoxysilane (s), metal alkoxide (s) and cerium cation Formed by an organic / inorganic mixed sol of metal alkoxide suitable for forming an organic / inorganic mixed matrix formed of inorganic atomic chains (—Si—O—Si—) and organic hydrocarbon chains by condensation. Apply the treatment solution.

  The inventors have not only allowed the formation of such a conversion layer and active protection against corrosion of the solid metal substrate by immersion of the solid metal substrate in the conversion solution, but also to the surface of the solid metal substrate. It has been found that it is possible to improve the adhesion of the mixed sol and the passive protective properties against corrosion of the solid metal substrate.

  According to the invention, advantageously, the corrosion inhibitor of the conversion solution comprises a lanthanum (La) cation, a cerium (Ce) cation, a praseodymium (Pr) cation, a neodymium (Nd) cation, a samarium (Sm) cation, a europium (Eu) cation. , Gadolinium (Gd) cation, terbium (Tb) cation, dysprosium (Dy) cation, holmium (Ho) cation, erbium (Er) cation, thulium (Tm) cation, ytterbium (Yb) cation and lutetium (Lu) cation Select from group.

  According to the present invention, the corrosion inhibitor of the conversion solution is advantageously selected from the group consisting of lanthanoid chloride, lanthanoid nitrate, lanthanoid acetate and lanthanoid sulfate.

Advantageously, each corrosion inhibitor of the conversion solution is lanthanum chloride (LaCl ₃ ), cerium chloride (CeCl ₃ ), yttrium chloride (YCl ₃ ), cerium sulfate (Ce ₂ (SO ₄ ) ₃ ), cerium acetate (Ce ( CH ₃ COO) ₃ ), praseodymium chloride (PrCl ₃ ), neodymium chloride (NdCl ₃ ).

According to the invention, advantageously, each corrosion inhibitor of the conversion solution is a cerium cation (especially cerium nitrate (Ce (NO ₃ ) ₃ ), cerium acetate (Ce (CH ₃ )) in which the cerium element is trivalent (Ce ^III ). COO) ₃ ), cerium sulfate (Ce ₂ (SO ₄ ) ₃ ) and cerium chloride (CeCl ₃ )).

According to the invention, advantageously, the cerium (Ce) cation of the treatment solution is selected from the group consisting of cerium chloride and cerium nitrate. In particular, the corrosion inhibitor of the conversion solution is cerium nitrate Ce (NO ₃ ) ₃ .

  The inventors have shown that the conversion layer is composed of a mixed oxide of cerium and the constituent metal of the oxidizable surface of the solid metal substrate. Chemical analysis by energy dispersive spectroscopy (“EDS, Energy Dispersive Spectroscopy”) shows characteristic Lα and Mα rays in cerium covalently bonded to the surface of a solid metal substrate.

  The present inventors are able to form an anticorrosion coating formed with a conversion layer suitable for allowing self-healing of a solid metal substrate comprising at least one corrosion inhibitor, by such an anticorrosion treatment method, It has been found that the conversion layer is itself protected by a cerium-rich mixed matrix that exhibits an optimal barrier effect.

However, the inventors also surprisingly found that the conversion layer is:
-Do not change the mechanical properties of the peel resistance and adhesion of the mixed matrix on the solid metal substrate,
-Do not change the barrier properties of the mixed matrix measured by EIS,
-The long-term immersion of the solid metal substrate in the corrosion bath can delay the loss of corrosion resistance of the solid metal substrate; and-the appearance of corrosion products on the metal substrate where the corrosion point has occurred. Delaying,
I noticed.

  The presence of a conversion layer rich in corrosion inhibitors, located at the interface between the solid metal substrate and the mixing matrix, can provide additional active protection in addition to the protective action of the mixing matrix.

  According to the invention, advantageously the conversion solution has a concentration of 0.001 mol / L to 0.5 mol / L, in particular 0.05 mol / L to 0.3 mol / L, in particular about 0.1 mol / L. The concentration of the corrosion inhibitor (especially cerium (Ce)) is indicated.

  Advantageously, the conversion solution has a concentration of corrosion inhibitor (especially cerium (Ce)) of 0.01 mol / L to 0.5 mol / L, preferably 0.1 mol / L to 0.5 mol / L. Show.

  Advantageously, the oxidizable surface of the solid metal substrate and the conversion solution are used for 1 second to 30 minutes, especially 1 second to 300 seconds, preferably 1 second to 15 seconds, especially 1 second to 10 seconds, more preferably. Stay in contact for a predetermined period of 1 to 3 seconds.

  Advantageously, after the step of contacting the oxidizable surface of the solid metal substrate with the conversion solution, the metal element M and M-O-Ln of the solid metal substrate, referred to as the conversion layer, are formed on the surface of the solid metal substrate. The solid metal substrate is dried at a predetermined temperature of less than 100 ° C. (especially about 50 ° C.) so as to form a layer of Ln (lanthanoid) element, a corrosion inhibitor bonded with —O— type bonds.

  Advantageously, the conversion solution exhibits a pH of approximately about 4. Advantageously, the pH of the conversion solution is adjusted by adding a mineral acid (particularly nitric acid) to the conversion solution.

  The inventors of the present invention provide a two-step solid metal substrate anticorrosion treatment method according to the present invention that provides active protection against solid metal substrate corrosion, particularly by repair, and further provides passive protection against corrosion. I also found that I can offer.

  According to the invention, the aqueous alcohol liquid composition is advantageously formed of water and at least one alcohol (especially selected from the group consisting of ethanol, 1-propanol and 2-propanol).

  Advantageously, the doped and / or physisorbed boehmite nanoparticles have one large dimension and two smaller dimensions perpendicular to each other and perpendicular to the large dimension, the large dimension Is less than 200 nm (especially less than 100 nm, especially less than 50 nm, preferably 5 nm to 20 nm) and the two smaller dimensions are less than 10 nm, preferably about 3 nm.

  According to the invention, the treatment solution advantageously comprises hollow boehmite nanoparticles at a loading.

  The invention is also directed to an anticorrosion coating obtainable by the method according to the invention.

The invention further extends to a solid metal substrate anticorrosion coating formed by a mixed matrix obtained by hydrolysis / condensation of at least one alkoxysilane spreading on the surface of the solid metal substrate.
The mixed matrix exhibits a silicon element molar ratio (Si / Ce) of alkoxysilane (s) to at least one cerium (Ce) cation of 50 to 500, in particular 80 to 250.

  This Ce / Si ratio is determined by means of methods known per se to the person skilled in the art, in particular the RBS of the elastic scattering of ions of the incident ion beam (Rutherford), which is suitable in particular for measuring the amount of heavy elements in a light mixing matrix Determined by backscatter spectroscopy analysis.

In particular, the present invention extends the mixed matrix in contact with a solid metal substrate and extends to at least one alkoxysilane and, optionally, an anticorrosion coating obtained by hydrolysis / condensation of at least one metal alkoxide, and at least One metal alkoxide is:
-At least one inorganic group represented by the general formula (IX):
-A-O-B- (IX)
(Where:
■ O is an oxygen atom,
(1) A and B are independently selected from the group consisting of Si and M ′), and at least one organic group represented by the general formula (XI):
-D-O-R ₁₀ -O-E- (XI)
(■ where O is an oxygen atom,
D and E are independently selected from the group consisting of Si, M ′ and Ce,
(1) R ₁₀ is a hydrocarbon group)
including.

  Advantageously, the anticorrosion coating is 1 μm to 15 μm thick.

The invention further extends to an anticorrosion coating exhibiting at least one of the following characteristics:
The mixed matrix of the anticorrosion coating is formed of a composite material comprising mixed xerogel (especially organic / inorganic mixed xerogel) and physisorbed boehmite nanoparticles dispersed in a loading of mixed xerogel;
The mixed matrix of the anticorrosion coating is a mixed xerogel (especially an organic / inorganic mixed xerogel) and a certain loading of the general formula (VIII):
Al _1-x (X) _x O (OH) (VIII)
(Where:
X is an element selected from the group consisting of trivalent lanthanoids (particularly trivalent cerium), referred to as doping elements,
X is a relative number between 0.002 and 0.01)
Wherein the certain loading is dispersed in the mixed xerogel,
The mixed matrix of the anticorrosion coating is formed of a composite material comprising mixed xerogel (especially organic / inorganic mixed xerogel) and hollow boehmite nanoparticles dispersed in a loading of mixed xerogel;
-A loading of solid adsorbed boehmite nanoparticles and doped boehmite nanoparticles of one loading is smaller than two larger dimensions, perpendicular to each other and perpendicular to said larger dimensions The larger dimension is less than 200 nm (especially less than 100 nm, especially less than 50 nm, preferably 5 nm to 20 nm), and the two smaller dimensions are less than 10 nm, preferably about 3 nm,
-A load of solid nanoparticles of hollow boehmite nanoparticles is approximately spherical in shape and has an average diameter of about 30 nm.

  Advantageously, the conversion layer of the anticorrosion coating is 1 nm to 200 nm thick.

  The invention further extends to metal surfaces coated with an anticorrosion coating obtained by the method according to the invention.

  The invention additionally relates to a method characterized by a combination of all or part of the features described above or below.

  Other objects, features and advantages of the present invention will become apparent upon reading the following description with reference to the accompanying drawings which represent preferred embodiments of the invention, given by way of non-limiting example only.

FIG. 1 is an enlarged schematic view of a variation of the anticorrosion coating according to the present invention. FIG. 2 is a scanning electron microscope observation (SEM) of the cross section of the anticorrosion coating on the solid metal substrate obtained by the method according to the present invention. FIG. 3 is a comparative graph showing the change in surface resistance to corrosion of a solid metal substrate treated by two variants of the method according to the invention. FIG. 4 is a graph showing the surface resistance (Ω · cm ² ) of the anticorrosion coating according to the cerium concentration in the treatment solution. FIG. 5 is a graph showing the Vickers nanohardness of the anticorrosion coating according to the cerium concentration in the treatment solution. FIG. 6 is a graph showing fluctuations in the Young's modulus value in GPa determined by measurement of nanoindentation. FIG. 7 shows the critical load values (mN) of peeling (◯), crack generation (▲), and elastic deformation (□) of the anticorrosion coating according to the cerium concentration in the treatment solution, determined by nanoscratching. It is a graph. FIG. 8 is a Nyquist representation of the electrochemical impedance of the solid metal substrate treated with the conversion solution (◯) or untreated (▲). FIG. 9 is a spectrum of chemical analysis of a surface of a solid metal substrate treated with a conversion solution according to the present invention by electron dispersion spectroscopy (“Energy Dispersive Spectroscopy (EDS)”).

  The anticorrosion coating 1 according to the present invention shown in FIG. 1 is supported on a metal substrate 2 formed of a metal element M. The anticorrosion coating is formed of an arbitrary conversion layer 3 in which the corrosion-inhibiting element Ln is bonded to the metal element M of the metal substrate 2 by a covalent bond M-O-Ln-. Further, the corrosion inhibiting element Ln of the conversion layer is a Si element and, if necessary, a metal element M ′ selected from the group consisting of aluminum (Al), vanadium (V), titanium (Ti) and zirconium (Zr). And a covalent bond is formed with the cerium (Ce) element of the mixed matrix 4 spreading on the surface of the conversion layer 3.

  FIG. 2 shows a scanning electron microscope observation of an aluminum substrate 2 which is processed by a variant of the method according to the invention and comprises a conversion layer 3 (optional) extending at the interface between the aluminum substrate 2 and the mixing matrix 4. The cross section by (SEM) is shown.

  In one variant of the anticorrosion treatment method for a solid metal substrate according to the present invention, first a surface pretreatment of a small piece of rolled aluminum alloy 2024 T3 is performed. Such pre-treatment is given only as a non-limiting example, and evenly applied to the substrate surface and on the substrate surface during the deposition ("dip coating", "spray") of the conversion solution and the treatment solution. The object is to remove from the solid metal substrate surface any traces of oxidation or fouling of the alloy that may impair the anchoring of the resulting anticorrosive mixed matrix.

The degreasing pretreatment of the solid metal substrate with an organic solvent includes a first step of degreasing the surface of the solid metal substrate, and in this step, the substrate surface is brought into contact with a degreasing solvent. This degreasing step is performed by a method known per se to those skilled in the art, in particular by immersing the substrate surface in a degreasing solvent, or by sprinkling the degreasing solvent on the surface.

  By way of example, the degreasing solvent may be stabilized pure methylene chloride (commercially available under the trademark Methoklone) or pure acetone. In this case, this degreasing step is performed at a temperature of less than 42 ° C. for a period of 5 seconds to 3 minutes. During the first step of degreasing, the solid metal substrate can be subjected to ultrasonic treatment.

Degreasing the solid metal substrate with an alkaline solution The pretreatment of the solid metal substrate comprises a second step followed by degreasing the surface of the substrate, wherein the substrate surface is treated with an alkaline preparation, in particular TURCO 4215 (HENKEL , Boulogne-Biencourt, France). This alkaline degreasing step is carried out by a method known per se to those skilled in the art, in particular by immersing the substrate surface in an alkaline preparation or by sprinkling the preparation on the surface for a period of 10 to 30 minutes. Preferably, the alkaline degreasing step is performed at a temperature of 50 ° C to 70 ° C. In the second step of degreasing with the alkaline solution, the substrate can be subjected to ultrasonic treatment.

Decontamination of Solid Metal Substrate with Alkaline Solution The pretreatment according to the invention comprises a third step followed by decontamination of the substrate surface, in which the substrate surface is treated with an alkaline preparation, in particular 30 g / L to 70 g. Contact with aqueous sodium hydroxide solution at a concentration of / L. This alkaline soil removal step is carried out by a method known per se to those skilled in the art, in particular by immersing the surface of the substrate in a concentrated alkali preparation or by sprinkling the concentrated alkali preparation on the surface for a period of 10 seconds to 3 minutes. To do. Preferably, the alkaline soil removal step is performed at a temperature of 20 ° C to 50 ° C. In the second step of removing dirt with the concentrated alkaline solution, the solid metal substrate can be subjected to ultrasonic treatment.

  At the end of this subsequent third step of treatment of the solid metal substrate surface, a powdered layer of oxide covering the solid metal substrate surface is observed.

Decontamination of solid metal substrate with acid solution The pretreatment according to the invention comprises a fourth step followed by dissolution of the oxide layer spreading on the surface of the solid metal substrate, wherein the substrate surface is treated with an acid preparation. For example, contact with TURCO LIQUID Smut-Go NC (HENKEL, Boulogne-Biencourt, France) or ARDROX 295 GD (Chemical GmbH, Frankfurt, Germany).

  This dissolution step is an aqueous solution containing 15% (v / v) to 25% (v / v) TURCO LIQUID Smut-Go NC, and is performed at a temperature of 10 ° C. to 50 ° C. for a period of 1 minute to 10 minutes. .

  In a variant, this dissolution step is an aqueous solution comprising 15% (v / v) to 30% (v / v) ARDROX 295 GD at a temperature of 10 ° C. to 30 ° C. for a period of 1 to 10 minutes. Do.

  At the end of this step, the solid metal substrate surface is suitable for being treated with an anticorrosion treatment according to the present invention.

  In one variation of the method for preventing corrosion of a solid metal substrate according to the present invention, a step of forming a conversion layer on the surface of the solid metal substrate is performed.

An aluminum piece (Al 2024-T3) containing Ce (NO ₃ ) ₃ at a concentration of 0.001 mol / L to 0.5 mol / L by “dip coating” and the pH was adjusted to 4 by addition of nitric acid. Soak in an aqueous conversion solution. After immersion and removal, the aluminum pieces are dried at 50 ° C. for 10 minutes. At the end of this treatment with the conversion solution, no increase in the mass of the aluminum pieces is measured.

In an anticorrosion treatment method for a solid metal substrate, a treatment solution is prepared according to the following steps:
-(A) Preparation of treatment solution as described in (A) below,
-(B) production of a colloidal dispersion of physisorbed boehmite nanoparticles as described in (B) below,
-(C) making a colloidal dispersion of doped boehmite nanoparticles as described in (C) below,
-(D) production of hollow aluminum oxyhydroxide nanoparticles containing corrosion inhibitors as described in (D) below,
-(E) preparation of a colloidal dispersion for anticorrosion treatment from a composition as described in (A), (B), (C) and (D) below,
-(F) deposition of a colloidal dispersion for anticorrosion treatment on a solid metal substrate,
-(G) Heat treatment.

A- Preparation of treatment solution-Epoxy sol A1- Epoxy sol GPTMS / ASB / Ce (NO ₃ ) ₃
In a first embodiment, 107.4 g (0.43 mol) of aluminum tri (s-butoxide) (ASB) was stirred into 34.8 mL of 1-propanol (especially to prepare 1 L of epoxy sol). Dissolve for 10 minutes at room temperature with magnetic stirring. 470 mL (2.13 mol) of 3- (glycidoxypropyl) -trimethoxysilane (GPTMS) is then added. The molar ratio of GPTMS to ASB is 83/17. Moreover, a cerium (III) (Ce (NO ₃ ) ₃ ) aqueous solution having a concentration of 0.02 mol / L to 0.5 mol / L was prepared, and a certain volume of the cerium aqueous solution was used as a precursor solution (ASB / GPTMS). To cause hydrolysis / condensation of the precursor. The resulting epoxy sol is placed under agitation for the time necessary to reduce the temperature to room temperature. The final concentration of cerium in the epoxy sol is 0.01 mol / L.

  On the aluminum substrate Al 2024-T3 pretreated as described above, an epoxy sol is deposited by dipping / removing the substrate into the epoxy sol. The take-off speed is 20 cm / min. The coated solid metal substrate is heated to a temperature of 95 ° C. to 180 ° C.—especially 110 ° C.—for a period of 1 hour to 5 hours—especially 3 hours. The formation of a 6 μm thick mixed matrix is observed on the surface of the solid metal substrate, indicating the duration for 96-800 hours of salt fog.

A2- epoxy sol TEOS / MAP / Ce (NO ₃ ) ₃
In a second embodiment, 230 mL tetraethoxysilane (TEOS) is added to 600 mL ethanol to prepare a 1 L mixed sol. Next, 30 mL of methacryloxypropyltrimethoxysilane (MAP) followed by an aqueous solution of cerium (III) (Ce (NO ₃ ) ₃ ) at a concentration of 4.32 g / L was added to hydrolyze the precursor TEOS and MAP Causes condensation. The obtained sol has a pH of 4.5 and a viscosity of 3 mPa · s.

B— Preparation of physisorbed colloidal boehmite nanoparticles A colloidal dispersion of boehmite nanoparticles with functionalized surfaces (referred to as physisorbed) is first formed into a colloidal solution of boehmite nanoparticles, then This is realized by the following two steps for functionalizing boehmite nanoparticles with a corrosion inhibitor.

B1- colloidal boehmite aluminum tri -sec-butoxide _{(ASB, Al (OH) x} (OC 4 H 9) 3-x) hydrolysis condensation Yoldas B. E. (J. Mater. Sri., (1975), 10, 1856), wherein an aluminum tri (s-butoxide) is heated to a temperature above 80 ° C. Add water. The resulting solution is left under stirring for 15 minutes.

  By way of example, such a solution of aluminum tri-sec butoxide is placed in water at a temperature of 80 ° C. for 15 minutes at a concentration of 0.475 mol / L (≈117 g / L). Next, a step called a peptization step is performed, and at that time, a 68% nitric acid solution having a volume of 1.4 mL to 2.8 mL is added to the hydrolysis solution of tri-sec butoxide. The mixture is placed in an oil bath at 85 ° C. for 24 hours. A colloidal dispersion of aluminum oxyhydroxide (boehmite) in water is obtained. The concentration of nitric acid in the colloidal dispersion is 0.033 mol / L to 0.066 mol / L. In a variant, the colloidal dispersion can be concentrated to a concentration of about 1 mol / L of aluminum oxyhydroxide. Other mineral acids or organic acids, in particular hydrochloric acid and acetic acid, may be used during this peptization step. A transparent and stable colloidal sol is obtained which exhibits the characteristic diffraction lines of boehmite described in sheet JCPDS 21-1307 by X-ray diffraction.

B2- Boehmite nanoparticles are functionalized with a colloidal dispersion obtained in accordance with Step B1 and exhibiting an aluminum concentration of 0.5 mol / L to 0.8 mol / L. (particularly 1% to 5% of the final weight percent of ^{Pluronic (R) P-123,} Pluronic (R) F127 (BASF, mount olive, NJ, USA), a non-selected from the group consisting of Brij 58 and Brij 52 Ionic surfactant) is added. Next, corrosion inhibitors, in particular cerium _{(III) (Ce (NO 3} ) 3) or a predetermined amount of sodium vanadate is added at a final concentration of 0.001 mol /L~0.5 mol / L. The preparation is left under stirring for a period of 6 hours at room temperature. A colloidal dispersion of boehmite nanoparticles with functionalized surfaces—referred to as physisorbed boehmite nanoparticles—is obtained. Such preparations may, by infrared spectroscopy using the a diffuse reflection technique DRIFT ( "Diffuse Reflectance Infra-red Fourrier Transform"), in the characteristic 1460 cm ^-1 and 1345cm ^-1 in coordination to nitrate cerium A vibration band is shown.

Preparation of a colloidal dispersion of C- doped boehmite nanoparticles Such a colloidal dispersion of doped boehmite nanoparticles is realized in the following two steps, in which the precursor of aluminum (especially alkoxide) and Hydrolysis / condensation (C1) of the corrosion inhibitor is performed. Next, a treatment step (C2) in an acidic medium, called a peptization step, is performed so as to form doped boehmite nanoparticles.

Hydrolysis / condensation of C1- ASB and (Ce (NO ₃ ) ₃ ) (especially aluminum alkoxides, especially aluminum tri (s-butoxide) (ASB)) and corrosion inhibitors (especially cerium (III) nitrate (Ce ( Hydrolysis / condensation of the mixture with NO ₃ ) ₃ )) is carried out by addition of minimal water heated to a temperature of 85 ° C. to this mixture. The hydrolysis / condensation mixture is left under stirring for 15 minutes. The final concentration of ASB in the hydrolysis / condensation mixture is 0.475 mol / L, and the final concentration of corrosion inhibitor in the hydrolysis / condensation mixture is 0.005 mol / L to 0.015 mol / L.

A C2- peptization hydrolysis / condensation mixture was added acidified aqueous solution (especially 68% nitric acid solution 1.4ML～2.8ML), 24 hours The acidified mixture 85 ° C. in an oil bath Put a period. The concentration of nitric acid in the acidified mixture is 0.033 mol / L to 0.066 mol / L. In a variant, the colloidal dispersion can be concentrated to a concentration of about 1 mol / L of aluminum oxyhydroxide. A transparent and stable colloidal sol is obtained which exhibits the characteristic diffraction lines of boehmite described in sheet JCPDS 21-1307 by X-ray diffraction.

D. Preparation of Hollow Aluminum Oxyhydroxide (Boehmite) Nanoparticles Containing Corrosion Inhibitors Hollow aluminum oxyhydroxide nanoparticles containing such corrosion inhibitors are formed in reverse phase microemulsions (Daniel H., et al ( 2007), Nano Lett., 7; 11, 3489-3492) and corrosion inhibitors.

  A nonpolar phase is prepared by mixing an alcohol (especially hexanol), an alkane (especially dodecane) and a surfactant (especially hexadecyltrimethylammonium bromide (CTAB)). A polar phase containing water, alcohol (especially methanol) and a corrosion inhibitor (especially cerium nitrate) is also prepared. The polar and nonpolar phases are mixed and the mixture is left under stirring for 30 minutes to form a reverse phase microemulsion of water in the nonpolar phase. Prepare a solution of aluminum alkoxide, in particular aluminum tri (s-butoxide) (ASB) in a volume of alkane, especially dodecane. Under stirring, a solution of aluminum alkoxide is introduced into the reverse phase microemulsion. The mixture is left for 12 hours. The residue containing hollow aluminum oxyhydroxide nanoparticles is separated by centrifugation. After the pellets are washed with diethylene glycol, hollow aluminum oxyhydroxide nanoparticle powders containing corrosion inhibitors are obtained.

E- Preparation of anti- corrosion treatment colloidal solution A certain amount of the anti-corrosion treatment colloidal dispersion of the treatment solution (mixed sol) prepared in (A), colloidal dispersion of physisorbed boehmite nanoparticles prepared in (B) And / or by mixing a certain amount of the colloidal dispersion of doped boehmite nanoparticles prepared in (C) and / or a certain amount of the colloidal dispersion of hollow boehmite nanoparticles. The concentration of aluminum and silicon in the anticorrosive colloidal dispersion is 1.66 mol / L to 2 mol / L. The concentration of aluminum provided by the colloidal dispersion of surface functionalized boehmite nanoparticles in the mixed sol is between 0.1 mol / L and 0.13 mol / L. The concentration of aluminum provided by the colloidal dispersion of doped boehmite nanoparticles in the mixed sol is between 0.1 mol / L and 0.13 mol / L. The mixed sol thus obtained is left at ambient temperature for a period of 24 hours.

  In an advantageous variant according to the invention, an alcohol solution containing at least one alkoxysilane and at least one aluminum alkoxide is prepared, and then the colloidal dispersion of physisorbed boehmite nanoparticles in the alcohol solution and / or Alternatively, an amount of a colloidal dispersion of doped boehmite nanoparticles and / or a colloidal dispersion of hollow boehmite nanoparticles is added.

  In this way, the viscosity of the treatment solution (dispersion), which is reduced by the addition of boehmite colloidal dispersion, is controlled. Thus, the thickness of the mixed gel deposited on the surface of the solid metal substrate is controlled, inter alia, according to the removal rate of the solid metal substrate from the treatment solution (dispersion).

F— Deposition of Colloidal Dispersion on Solid Metal Substrate Deposition process of colloidal dispersion for anticorrosion treatment on the surface of a solid metal substrate, in particular on the surface of a piece of rolled aluminum alloy 2024 T3 previously degreased and soiled I do. During this deposition process, part of the solvent of the composite mixed sol evaporates, and at the same time, an anticorrosive composite on the surface of the solid metal substrate by hydrolysis / condensation of the alkoxysilane (s) and metal alkoxide (s). A mixed matrix can be formed.

The presence of cerium as a corrosion inhibitor in the treatment solution, in particular free cerium (Ce ^III ), enables the formation of a chemically stable conversion layer in the corrosive medium during the deposition of the solution. Such a conversion layer is formed, inter alia, from the hydroxyl group of the constituent element M of the solid metal substrate, which forms M—O—Ce— bonds with cerium.

  The presence of physisorbed boehmite nanoparticles and doped boehmite nanoparticles in the treatment solution is suitable to allow the formation of a reservoir of corrosion inhibitors in the composite mixed matrix that constitutes the anticorrosion coating, said reservoir Is suitable to allow controlled release of corrosion inhibitors over time.

  Application of the treatment solution to the surface of the solid metal substrate can be carried out by any means known per se to the person skilled in the art, in particular by immersion / removal (“dip coating”), by spraying (“spray coating”) or by solid metal substrates. By applying with a brush, tampon or brush for local use as a repair of the surface coating.

  With respect to immersion / removal techniques, the removal rate can control the deposition thickness of the treatment solution at a given viscosity of the treatment solution. Typically, the removal rate is in the range of 2 to 53 cm / min. Application of multiple layers by successive dipping / removing operations, with a drying step after each dipping / removing operation, allows the formation of increased thickness coatings as needed.

  In addition, during the dipping process, in order to promote a chemical reaction between the solid metal substrate and the treatment solution, it is possible to extend the residence period of the solid metal substrate in the treatment solution. As an example, the extended residence time may be in the range of 1 to 300 seconds.

  For spraying techniques, the deposition thickness is the viscosity of the treatment solution, spray parameters, especially pressure, flow rate, spray nozzle geometry, and nozzle movement speed relative to the solid metal substrate surface, and the solid metal substrate surface. Is controlled by the number of times the nozzle passes in front of the nozzle. Application of the treatment solution may be performed manually or may be automated according to conventional techniques.

  For manual application techniques with a brush, tampon or brush, the deposition thickness is controlled by the viscosity of the treatment solution and by the number of consecutive applications to the surface of the solid metal substrate.

  This process solution deposition process on the surface of a solid metal substrate is particularly controlled in atmosphere and humidity to limit the overly rapid evaporation of the solvent (s) and to limit contamination of the atmosphere. Can be done in enclosed spaces.

  In the process according to the invention, it is also possible to carry out the process solution deposition step in an open space, in particular by spraying in the open space.

The residual solvent (s) of the G- heat treatment solution are removed by evaporation and the treatment solution applied to the surface of the solid metal substrate is heat treated to allow its polymerization into a composite mixed matrix. In particular, such a heat treatment comprises two successive steps, in which the solid metal substrate coated with the treatment solution is first subjected to a first at a temperature of 50 ° C. to 70 ° C. for a period of 2 hours to 24 hours. Subject to a heating step, said first heating step being suitable to allow removal of aqueous solvent and / or organic cation, and then a first temperature at 110 ° C. to 180 ° C. for a period of 3 hours to 16 hours. The second heating step is suitable for completing the polymerization of the treatment solution and for improving the mechanical properties of the composite mixing matrix.

  FIG. 3 represents the variation of the surface resistance of a solid metal substrate treated with the method according to the invention as a function of the immersion time in the corrosion bath (0.05 mol / L NaCl in water) of this solid metal substrate. ing. The curve (●) shows a solid metal treated according to the procedure according to the invention consisting of a continuous application of a cerium rich (0.1 mol / L) conversion solution and then a treatment solution containing cerium (0.01 mol / L). It represents the variation of the surface resistance of the substrate. The surface resistance (●) of the treated solid metal substrate is slower than the surface resistance (△) of the solid metal substrate treated with the same treatment solution (0.01 mol / L Ce) but without the conversion layer. It is observed that

表1 The numerical values are shown in Table 1 below.

table 1

In particular, after 48 hours of immersion in a corrosion bath, the surface resistance (Δ) of the untreated substrate reaches a value of about 2.12 · 10 ⁶ Ω · cm ² , while the surface of the treated substrate It can be seen that the resistance (●) stops at about 4.05 · 10 ⁶ Ω · cm ² . After 72 hours of immersion in a corrosion bath, the surface resistance (Δ) of the untreated substrate reaches a limit value of about 1.1 · 10 ⁶ Ω · cm ² , while the surface resistance of the treated substrate (●) stops at about 2.75 · 10 ⁶ Ω · cm ² .

  The inventors have also quite unexpectedly and surprisingly provided anticorrosion treatment of solid metal substrates according to the invention with a treatment solution containing cerium in a concentration of 0.005 mol / L to 0.015 mol / L. Electrochemical impedance spectroscopy optimal for immersion periods of 1 day (△), 7 days (◯) and 14 days (●) in a corrosion bath in a 0.05 mol / L NaCl aqueous solution of a solid metal substrate Not only was it possible to obtain the surface resistance of the anticorrosion coating, measured by the method (FIG. 4), but this treatment also allowed for this maximum nanohardness (FIG. 5), Young's modulus (FIG. 6) and anti-peeling It has been found that it is possible to obtain the limit values (□, FIG. 7) of the property (◯, FIG. 7), crack resistance (▲, FIG. 7) and plastic resistance.

  Corrosion resistance of the solid metal substrate Al 2024-T3 treated with conversion solution or untreated and then exposed to a corrosion process by immersion in 0.05 mol / L NaCl aqueous solution is determined as electrochemical impedance. Analyze by spectroscopy. The results are shown in FIG. 8 according to the Nyquist display.

Treatment of the aluminum pieces 2024-T3 treated with the conversion solution by immersion in a corrosive solution (NaCl 0.05 mol / L) at ambient temperature for 30 minutes resulted in about 4.10 ⁴ Ω · cm ^{2 on the} aluminum pieces. The surface resistance Z ′ indicated by “Nyquist” is given (◯, FIG. 8). As a comparison, immersion of the crude aluminum piece 2024-T3 (ie, not treated with the conversion solution) in a corrosive solution gives the aluminum piece a surface resistance Z ′ of about 5 · 10 ³ Ω · cm ² (▲ FIG. 8).

The treatment of aluminum piece 2024-T3 without prior immersion in a conversion solution formed with water and cerium (0.01 mol / L) and without immersion in a corrosion bath is 6 · 10 ⁵ Ω · cm ^2. A surface resistance Z ′ of a value exceeding Increasing the immersion period in the corrosion bath up to 168 hours returns the surface resistance of the aluminum pieces to the characteristic value of the aluminum oxide layer of about 5 · 10 ³ Ω · cm ² .

  Increasing the cerium concentration in the conversion solution and increasing the immersion period of the aluminum metal piece in the conversion solution results in an increase in the surface resistance of the aluminum metal piece.

In particular, the residual surface resistance Z ′ of such aluminum pieces after 1 hour immersion in a corrosive solution is about 1.1 · 10 for a cerium concentration of 0.01 mol / L in the conversion solution and a conversion treatment period of 1 second. ⁴ Ω · cm ² , cerium concentration in conversion solution 0.05 mol / L, and about 2 · 10 ⁴ Ω · cm ² for conversion treatment period 1 second, cerium concentration 0.1 mol / L in conversion solution and conversion The processing period is about 3.3 · 10 ⁴ Ω · cm ² for 1 second.

The residual surface resistance Z ′ after immersion of the aluminum piece in the corrosive solution for 1 hour is about 1.1 · 10 ⁴ Ω · for a cerium concentration of 0.01 mol / L in the conversion solution and for a conversion treatment period of 1 second. cm ² , a cerium concentration of 0.01 mol / L in the conversion solution and about 2 · 10 ⁴ Ω · cm ² for a conversion treatment period of 60 seconds, a cerium concentration of 0.01 mol / L in the conversion solution and a conversion treatment period of 300 The second is about 3.8 · 10 ⁴ Ω · cm ² .

The residual surface resistance Z ′ after immersion of the aluminum piece in the corrosive solution for 1 hour is about 3.2 · 10 ⁴ Ω · for a cerium concentration of 0.1 mol / L in the conversion solution and for a conversion treatment period of 1 second. cm ² , cerium concentration 0.1 mol / L in the conversion solution and about 4.0 · 10 ⁴ Ω · cm ² for the conversion treatment period of 60 seconds, cerium concentration 0.1 mol / L in the conversion solution and conversion treatment It is about 9.0 · 10 ⁴ Ω · cm ² for a period of 300 seconds. The prolonged immersion in the corrosion bath results in a decrease in the surface resistance value, reaching the surface resistance value of aluminum oxide in 10 hours.

The surface resistance Z ′ of the aluminum pieces treated with a conversion solution containing cerium at a concentration of 0.5 mol / L for a period of 1 second, 60 seconds and 300 seconds is 40 hours, 70 minutes for the aluminum pieces in the corrosion bath, respectively. It remains above 1 · 10 ⁴ Ω · cm ² after soaking for 90 hours.

  Chemical analysis by EDS (FIG. 9) can show the presence of cerium Ce (III) on the surface of a solid metal substrate treated with a conversion solution containing cerium at a concentration of 0.5 mol / L for 300 seconds. The main signal is characteristic of an aluminum substrate.

Claims (12)

On an oxidizable surface of a solid metal substrate, in a hydroalcoholic liquid composition; and at least one alkoxysilane, and
At least one cerium (Ce) cation,
A solution called a treatment solution is applied, and the treatment solution forms a mixed matrix on the surface of the solid metal substrate by hydrolysis / condensation of each alkoxysilane (s) and each cerium (Ce) cation. Is suitable for
The treatment solution is an anticorrosion treatment method in which a molar ratio (Si / Ce) of the silicon element of the alkoxysilane (s) to the cerium (Ce) cation (s) is 50 to 500,
A method wherein the cerium (Ce) cation (s) exhibits a concentration of 0.005 mol / L to 0.015 mol / L in the treatment solution. Each alkoxysilane:
The following general formula (I)
Si (O—R ₁ ) ₄ (I)
(Where:
Si is a silicon element, O is an oxygen atom,
R ₁ is:
( ₁ ) A hydrocarbon group represented by the formula [—C _n H _{2n + 1} ] (wherein n is an integer of 1 or more),
■ 2-hydroxyethyl group _{(HO-CH 2 -CH 2 -} ), and ■ the general formula 'acyl group (wherein represented by _1, R' -CO-R ₁ in the formula _{[-C n H 2n + 1]} And n is an integer of 1 or more),
Selected from the group consisting of
Tetraalkoxysilane represented by:
The following general formula (II):
Si (O—R ₂ ) _4-a (R ₃ ) _a (II)
(Where:
R ₂ is:
( ₁ ) A hydrocarbon group represented by the formula [—C _n H _{2n + 1} ] (wherein n is an integer of 1 or more),
■ 2-hydroxyethyl group _{(HO-CH 2 -CH 2 -} ), and ■ the general formula 'acyl group (wherein represented by _1, R' -CO-R ₁ in the formula _{[-C n H 2n + 1]} And n is an integer of 1 or more)
Selected from the group consisting of
R ₃ is an organic group bonded to the silicon element (Si) of alkoxysilane by a Si—C bond,
A is a natural number in the range] 0,4 [)
The method according to claim 1, wherein the method is selected from the group consisting of alkoxysilanes represented by:   The method according to claim 1, wherein the treatment solution comprises at least one metal alkoxide. Each metal alkoxide has the following general formula (VII):
M ′ (O—R ₉ ) _{n ″} (VII)
(Where:
M ′ is a metal element selected from the group consisting of aluminum (Al), vanadium (V), titanium (Ti) and zirconium (Zr),
R ₉ is an aliphatic hydrocarbon group represented by the formula [—C _n H _{2n + 1} ] (wherein n is an integer of 1 or more),
N ″ is a natural number representing the valence of the metal element M ′)
The method of claim 3, wherein: Each metal alkoxide has the following general formula (III):
Al (OR ₄ ) _n (III)
(Where:
Al and O are aluminum element and oxygen element, respectively
R ₄ is an aliphatic hydrocarbon group having 1 to 10 carbon atoms,
(N is a natural number representing the valence of the aluminum element (Al))
The method according to claim 3, wherein the aluminum alkoxide is represented by:   6. The method according to any one of claims 1 to 5, characterized in that the solid metal substrate is formed of a material selected from the group consisting of oxidizable materials.   Prior to applying the treatment solution, the oxidizable surface of the solid metal substrate is immersed in a solution called a conversion solution formed of at least one corrosion inhibitor in water, the corrosion inhibitor comprising lanthanoid cations. The oxidizable surface of the solid metal substrate selected from the group is formed with the conversion solution and the lanthanoid bonded to the oxidizable surface by at least one covalent bond and spreads on the surface of the solid metal substrate 7. A method according to any one of the preceding claims, characterized in that it remains in contact for a period suitable for forming the conversion layer.   The method according to claim 7, wherein the conversion solution exhibits a corrosion inhibitor concentration of 0.001 mol / L to 0.5 mol / L.   9. The method according to any one of claims 1 to 8, characterized in that the treatment solution is applied by dipping / removing the solid metal substrate into the treatment solution.   The method according to claim 1, wherein the treatment solution is applied by atmospheric spraying of the treatment solution onto the surface of the solid metal substrate.   The method according to claim 1, wherein the aqueous alcohol composition is formed of water and at least one alcohol.   12. A method according to any one of the preceding claims, characterized in that the cerium cation of the treatment solution is selected from the group consisting of cerium chloride and cerium nitrate.

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