EP2697346A1

EP2697346A1 - Process for the protective treatment of metals based on a water-soluble composition of saponified plant oil(s), and products and compositions obtained

Info

Publication number: EP2697346A1
Application number: EP12724704.7A
Authority: EP
Inventors: Jean Pierre Philippe LARONZE; Emmanuel Rocca; Delphine RENAUX
Original assignee: Laboratoires Labema; Universite de Lorraine
Current assignee: Laboratoires Labema; Universite de Lorraine
Priority date: 2011-04-13
Filing date: 2012-04-06
Publication date: 2014-02-19
Also published as: FR2974112A1; FR2974112B1; WO2012140488A1

Abstract

The present invention relates to an anticorrosion composition for the "metals" consisting of or comprising at least one saponification product of at least one plant oil, or mixture of plant oils, the plant oil or oils comprising "C14-C22" carbon atom chains, a process for manufacturing, in a single reactor ("one-pot" process) a saponified plant oil composition, products and compositions resulting from this process and the uses thereof.

Description

Process for the treatment of metals based on the water-soluble composition of saponified vegetable oil (s), and products and compositions obtained

TECHNICAL SECTOR

The present invention relates to the technical field of anticorrosive chemistry and in particular for applications of corrosion inhibitors, in the "coating" ("coating"), the temporary protection or not of metals, anticorrosive fluids, and more generally, in all areas where corrosion activity is sought on metals.

PRIOR ART

In the field of anticorrosion, various types of thin film coatings, more or less impermeable to air and water have been developed. These coatings are generally used either in the field of the temporary protection against corrosion of metal parts during storage under shelter or transport, or to protect the metal elements present in the cooling water circuits, heating, washing or lubrication.

This type of treatment process should be easy to apply and non-toxic. The coating must also be easy to remove from the parts without producing additional pollution, altering the surface condition of the supports, or discomfort during their handling.

For this, the application on metal surfaces or "metals" of several types of protection solutions is mentioned in the state of the art:

Oily or semi-oily compositions obtained by mixing water and mineral oil in emulsion are called "white emulsions". These solutions often contain a corrosion inhibitor as in US Pat. No. 4,342,596.

More complex emulsions comprising mineral paraffins, amides, alcohols and surfactants described in US Pat. No. 4,479,981. can also be used (patent WO 06/070083 A1). Other temporary protective coatings are obtained by spraying, on the surface to be protected from atmospheric air, water-soluble compositions obtained by mixing polyoxyalkylene glycols and alkyl derivatives of succinic anhydride, such as the composition described in US Pat. U.S. Patent 5,316,696.

The coatings formed are presented as having good stability and may be a good barrier to atmospheric oxidation, but result in the formation of an oily and liquid film on the surface of the parts, and many liquid effluents and volatile organic compounds in the workshops, often difficult to process. Recently, certain carboxylic acid or carboxylate salt compositions have been patented as an inhibitor of atmospheric corrosion. The carboxylic acids used are linear acids of chemical formula:

and are denoted HC _n with 7 <n <11.

The notation HCn corresponds to the formula

CH ₂ = CH- (CH ₂ ) ₈ COOH.

The thin films formed with these solutions have the advantage of having a "dry appearance" of being easily removable from the surface and generating little pollution. They are described by EP 0556 087A1.

Some authors mention the possibility of using carboxylic acids or carboxylates with long carbon chains (up to 18-22 carbons) in complex formulations comprising volatile organic solvents and / or surfactants which are difficult to biodegradable (patent WO 02/077324 A3) .

TECHNICAL PROBLEM

Environmental regulations on effluents discharged by industrial plants, hygiene and safety requirements and increased productivity impose complex specifications:

- simple application process by immersion, spraying or coating,

- an aqueous composition free of volatile organic compounds (organic solvent) and surfactants in order to avoid the use of expensive effluent treatment systems,

- easy use of treatment solutions by simple dilution in water of a concentrated solution, to facilitate the storage and transport of solutions.

- good corrosion resistance of the "dry" film formed.

As shown in the state of the art, the linear carboxylic acids of formula CH ₃ (CH ₂ ) _n - ₂ COOH and the associated carboxylate ions, with or without unsaturations, are compounds of interest for forming "dry" films ( or non-oily) on metals. However, two industrial constraints currently impose limiting these processes to the use of short chain carboxylic acids, less than or equal to 10-12 carbons:

the need to provide a concentrated liquid product (with a maximum viscosity of 100 to 150 centipoise (cPo) at 20 ° C) to facilitate storage, transport, and dilution,

the need to propose a totally aqueous product, without organic co-solvents such as alcohols, and without surfactants which can give rise to effluent treatment problems in the treatment plant.

In addition, the complex formulations based on surfactant and / or co-solvent often cause problems of stability of the baths in service such as phase separations (demixing), solid deposits in the bottom of the tank, or bacterial developments.

In addition to the technical problems of manufacture and / or service of these formulations, films "liquid" or formed from short-chain carboxylic acids have a limited resistance to corrosion under atmospheric corrosion conditions commonly encountered during storage. metal parts under cover or during transport. Indeed, the moisture recovery in the stacks of parts leads to severe differential aeration conditions and corrosion inside the stack. In addition, the industrial conditions of use require that the solution can dry in the open air without causing the appearance of corrosion products (red rust on iron bases or white rust on galvanized products or tarnishing on copper products or based on aluminum).

In the field of temporary protection and aqueous anticorrosive additives, the objective technical problem is therefore to use, if possible, carboxylic acids and / or carboxylate salts with long carbon chains (HC _n with n> 14) in order to to increase the stability of the protective film in fully aqueous formulations, that is to say without any co-solvent or any of the now-regulated defects of the prior art AND provided they are used in the context of a formulation and a method which avoids the aforementioned drawbacks. These formulations should also be prepared concentrated (for transport and storage) and then be easily diluted in water.

The merit of the invention is, moreover, to have overcome the prejudgment which was attached a priori to the solution developed below by a process and totally original compositions.

SUMMARY OF THE INVENTION

The present invention aims to meet this technical challenge from saponification products in general, provided that they meet the above criteria, including aqueous reaction medium and long chain carboxylic acids, we do not duplicate not here. This approach had never been attempted or considered in the state of the art. It relates more particularly, according to a clearly preferred but non-limiting mode, an innovative saponification process in dilute medium, a corresponding saponification product, said saponification process preferably employing reagents from eco-resources, including oils plant.

This saponification process, according to the present invention, makes it possible to prepare in aqueous solvent concentrated solutions of carboxylic acids with long carbon chains up to 250 g / l (HC _n with n> 14) usable for the targeted treatment. This process, referred to as a "one-pot process", requires a single reactor in which reagents are added successively, and requires no separation, purification or transfer of material steps. In addition, no addition of organic solvents or co-solvents (still sometimes called humectants) is necessary to achieve the desired viscosity.

This method of forming a "dry" anti-corrosion film, according to the present invention, is done by simple application on the metal surfaces or "metals" (immersion, spraying or coating) of a totally aqueous solution (without organic solvent and surfactant). active), prepared from this method of saponification in a diluted medium. This "dry" film has anti-corrosion properties on metals due to its insoluble nature in water and hydrophobic (weak wettability).

The present invention comprises the innovative saponification process, as well as the application of the anti-corrosion solution obtained, and the solution or protection composition used / applied, and their applications to anticorrosion.

In a manner wholly known to those skilled in the art, the saponification in a basic medium in order to create a liquid soap is carried out according to the following steps:

saponification (which is a chemical reaction allowing the transformation of an ester into a carboxylate ion and an alcohol),

- maturation (very slow, duration approximately 8 to 15 days, or more),

- recovery of the mass by water.

During this reaction, the fatty substances (fat or oils) are hydrolysed in an alkaline medium with a base, usually sodium hydroxide (NaOH) or potassium hydroxide (KOH), at a temperature of between 30 ° C. and 80 ° C. . The elevated temperature serves to accelerate the saponification reaction. The saponification of fatty substances produces glycerol and a mixture of carboxylates (sodium or potassium) which constitutes the soap.

The above is known and will not be described in more detail here.

All known methods of saponification in the prior art have either: - discontinuous processes very long to implement (more than fifteen days): These processes are carried out in a traditional way and therefore extremely difficult to industrialize, in particular because of fact that the recovery of the compact mass, to heat and dilute is extremely difficult to achieve on large volumes. In this context, the skilled person, so far, could effectively treat only small volumes.

- continuous processes carried out under hydrothermal conditions:

These saponification processes are commonly used to make many soaps and operate at high temperature (up to 250 ° C) and under pressure (up to 20 bar). [Ref: T. Ogoshi and Y. Miyawaki Journal of the American Oil Chemists' Society Volume 62, Number 2, 331-335, DOI: 10.1007 / BF02541400]. Although they are continuous processes, these processes are not "one pot" (or implemented in a single reactor) and require material transfer operations, heavy industrial resources and large investments (boiler room, steam production , means of pumping ...). In addition, the use of high temperatures and high pressures is much too expensive for the intended application.

The prior art therefore proposes in terms of saponification only:

- manufacturing processes too slow to be able to envisage important productions,

- processes requiring excessive investments for the intended application,

industrial processes that do not make it possible to obtain sufficiently liquid soap solutions.

One of the merits of the Applicant is, after considering a product corrosion resistant saponification, already not obvious in the light of the prior art, despite having developed an effective and simple method deviating in particular previous multi-step processes, while proposing a solution which can also correspond to the specifications of an anti-corrosion solution and to the industrial and ecological criteria:

- low energy consumption and no addition of organic solvents or co-solvents (or humectants) to improve fluidity,

- industrial investment limited to a single agitated and thermostatically controlled reactor.

composition, in particular concentrated aqueous solution (up to 250 g / l of carboxylic acids containing from 14 to 22 carbons, that is to say having stable "C14-C22" chains and liquid (viscosity <150 cPo to 20 ° C).

It is known to those skilled in the art that oils are generally composed of a mixture of chain length products that may be different from one another.

Throughout the present application, including the claims, "C14-C22" will be understood to mean oils or mixtures of oils comprising either only C14 to C22 chains or very predominantly C14-C22 chains, especially preferably greater than or equal to 80%, preferably greater than or equal to 90%, and more preferably greater than or equal to 95%, the only criterion being that, according to the invention, an extremely clear solution is obtained extremely preferably stable and concentrated saponification product incorporating said carboxylate chains. It is therefore possible to tolerate a small percentage, preferably a very small percentage, in the starting oil (s), for example, C12 or C10, or, in theory, C24 or C26.

The skilled person will appreciate this very slight nuance and adapt it to his particular case with no other task than a few routine tests.

In some cases, the skilled person calls "waxes" oils in particular C22, C24, C26 but throughout the present application including the claims will be used only the term "oils" for simplicity.

DETAILED DESCRIPTION OF THE INVENTION

The object of the present invention is therefore to develop a composition, a product and a method for the anticorrosion treatment of metal parts (hereinafter "metals") by application of an aqueous solution obtained by saponification, and in particular saponification of vegetable oil, diluted medium.

In the present invention, the term "metals" means the group formed by iron and its alloys; Copper and its alloys; Aluminum and its alloys, Zinc and its alloys; Lead and its alloys; tin and its alloys; including all of these partially oxidized or corroded metals.

According to the preferred embodiment, the aqueous solution applied is obtained by dilution between 0.2 and 30% by weight of a concentrated solution obtained by saponification in a dilute medium of vegetable oil (s).

The method of manufacture (by saponification according to the invention) of the concentrated solution (or composition) must be rapid, "reproducible", that is to say be able to be industrialized, and lead to a product with a pH and a viscosity conform to industry standards.

The concentrated solution of the product or composition must be chemically stable without the addition of organic and / or surfactant co-solvents, and be biologically stable, without the addition of bactericidal compounds having a toxic character.

In a very advantageous manner, and this is one of the notable advantages of the invention, the process is implemented extremely preferably in "one pot" mode, but could, with obvious industrial disadvantages, be realized in two reactors. . However, the Applicant does not see the point.

The dilute aqueous solution applied to the metal surfaces must be allowed to air-dry at room temperature or hot air on the parts without rinsing. It must allow corrosion protection in conventional atmospheric conditions under shelter (alternation of dry and wet periods) and in stacking conditions of metal parts generating corrosion phenomena by differential aeration. The present invention therefore relates to a method of anticorrosion treatment from a solution developed from a saponification process, and in particular a very preferred saponification process, described hereinafter in detail, and completely innovative.

The first subject of the invention is the anticorrosion composition for "metals", characterized in that it consists or comprises at least one saponification product of at least one vegetable oil, or mixture of vegetable oils (or, so to speak equivalent throughout this application, "composition") and the "one-pot" process (or extremely preferred implementation in a single reactor) allowing the manufacture of a concentrated saponified solution (in other words product derived from saponification) without the stages of maturation, storage, recovery that required a lot of time. The process is carried out at atmospheric pressure, at a temperature between 70 ° C and 99.9 ° C (boiling limit at atmospheric pressure) and without the use of water vapor, and uses at least one vegetable oil as a product of departure.

To do this, the Applicant has considered a large number of different oils (including Sweet Almond, Peanut, Avocado, Shea, Flax, Olive, Sunflower, Palm, Rapeseed, Apricot Kernels, Corn, Ricin), used alone or in combination. mixed.

The Applicant has finally selected the use of castor oil which alone (among the oils tested) and surprisingly, allows to obtain a sufficiently concentrated solution, limpid and stable.

The other oils tested lead to products in the form of more or less thick paste physico-chemical form which is not the clear and stable solution particularly targeted by the present invention. However, these pastes nevertheless have an anticorrosion power but are industrial applications much less interesting than a stable and clear solution.

The preferred method is detailed as follows:

a) In a first phase, a quantity of vegetable oil (between 15 and 35% by weight of the final mixture) is mixed with a potassium hydroxide solution (between 5 and 20% by weight of the final mixture).

The mixture is heated under constant stirring at a temperature between 70 ° C and 99.9 ° C (boiling limit at atmospheric pressure) at atmospheric pressure, for 15 to 30 min.

It will naturally be possible to use any type of base suitable for saponification, accessible to those skilled in the art.

At this stage, in the prior art, in conventional saponification processes, after heating, those skilled in the art stopped stirring and allowed the mixture to cool for ripening. b) In the place of the maturation phase, the Applicant prepares a quantity of water representing between 50 and 80% by weight of the final mixture (preferably between 45 and 80% of the final mixture) heated between 70 ° C and 99, 9 ° C (boiling limit at atmospheric pressure) at atmospheric pressure, then performs steps c and d. c) The hot water prepared under b) is then incorporated into the composition obtained in step a) with constant stirring taking care not to form bubbles. d) The new mixture is then cooled down to the temperature of use.

Preferably, the temperature chosen in the different steps of the process is between 95 ° C. and 99.9 ° C., very preferably it is between 85 ° C. and 95 ° C., and finally, less preferably, it is between 70 ° C and 85 ° C still at atmospheric pressure.

The final mixture (which is the product or composition according to the invention) is completely transparent, directly has the desired viscosity (about 100 to 150cPo). The saponification is complete (no rise of oil appears), and the saponification product in solution is excessively stable over time (more than 12 months without addition of organic co-solvent or surfactant).

The total process (instead of the 15 days required for the prior art) is carried out in a single reactor on a working day at most.

The set is therefore very different from the prior art of saponification, and totally innovative. The product obtained is also innovative by the absence of solvent and other advantageous properties.

The Applicant has thus achieved thanks to its original process to integrate in the saponification of the carboxylate chains in "C14-C22", which one would have wished to be able to use in the prior art but that the prior art is never managed to use.

Depending on the type of metal to be protected and the contact time between the solution and the metal surface (residence time of the solution), the solution thus created may be supplemented with oxidizing or accelerating agents such as nitrite salts. nitrates, persulfates, perborates, percarbonates or hydrogen peroxide. It will be preferred to add 1 to 20% by weight of hydrogen peroxide for its non-toxic nature and harmless to the environment.

Those skilled in the art will naturally be able to add other products at the end of the process aimed at providing additional desired characteristics, for example: an antifoaming agent, and / or

- 0.002% to 2% (by weight) of a wetting agent selected from the group consisting of anionic surfactants such as alkylsulfates and nonionic surfactants such as ethoxylated compounds of the fatty alcohol type and alkylphenols, facilitating the spreading solution on metal surfaces (example: 1% lauryl sulphate), and / or

0.2 to 5% (by weight) of an additional compound having corrosion inhibiting properties such as the triazol derivatives chosen from the group consisting of benzotriazoles, tolyltriazoles and alkyltriazoles. (example: 1% tolyltriazole), and / or

additional bactericidal / fungicidal compounds,

- one or more acid-base compounds, allowing a better stability in pH (buffer solution) (eg addition of 0.01 mol / l Na2B4O7,10H ₂ O).

The skilled person may also add from 0.2 to 20% by weight of an oxidizing compound or accelerator.

This is well known to those skilled in the field of anti-corrosion.

The method according to the invention therefore leads to a "final mixture" which is the "product according to the invention", which becomes a "composition according to the invention" after the possible additions above. It may be of great interest to work the concentration of said composition, in particular dilute it to the usual application concentration in anti-corrosion.

A much less preferred alternative is to put all the ingredients together and brew and heat longer. According to the tests of the Applicant, it takes 2 to 6 times more time for a result not always interesting (including oil up).

The invention also covers the "products" and "compositions" obtained by the process according to the invention with the possible addition of subsequent additives as described above.

The second object of the invention is the method of depositing and forming the protective film on the metal surfaces from said concentrated composition. It consists in diluting the said solution between 0.2 and 30% by weight in water, bringing the solution thus formed into contact with the metal surface for residence times ranging from 10 seconds to 24 hours, to drain the so-called solution and then dry the said surface in the open air or under a possibly heated air stream.

To bring the solution formed into contact with the metal surface, any means will be used, in particular watering, spraying or immersion. The film thus obtained is in the form of a non-oily dry film which does not stick and which leaves no dirt on the hands during the handling of the metal parts and which protects them from atmospheric corrosion.

A third object of the invention is the use of these concentrated compositions to form dry films for the particular protection against corrosion of metal surfaces or "metals" including iron and its alloys; Copper and its alloys; Aluminum and its alloys, Zinc and its alloys; Lead and its alloys; tin and its alloys; including all of these partly corroded metals.

In order to modify the pH of the solution obtained (for example close to a pH of 8.5), the person skilled in the art may optionally optionally add, at the end of step d), as a neutralizer, an acidic compound such as a carboxylic acid or borax. Benzoic acid is preferred because it provides bactericidal properties, very useful for the preservation of the final product, on the other hand it increases the effectiveness on corrosion. Other acids, having little or no influence at low concentration on the anticorrosion properties, can be used as including heptanoic acid, undecylenic acid, benzoic acid, etc.

It is of course quite possible to choose other mineral acids such as phosphoric or sulfuric acids, etc. which will be easily accessible to those skilled in the art with the help of this knowledge and routine tests.

Figure 1 which consists of Figures 1a-1d shows the measurement of corrosion potential (1a and 1b) and corrosion rates by the polarization resistance method (1c and 1d) in ASTM-free water or with solutions 1, 2, or 3 of Table 1.

Figure 2, which consists of Figures 2a to 2c, shows the results of the test DIN 51360 (black areas correspond to corroded areas).

Figure 2a shows the visual result of the degree of rust without the additive.

Figure 2b shows the visual result of the degree of rust with solution 1

(Table 1) with a dilution in the corrosive solution of 5% (by mass).

Figure 2c shows the visual result of the degree of rust with solution 4

(Table 1) with a dilution in the corrosive solution of 5% (by mass).

Figure 3 consists of Figures 3a to 3c.

Figure 3a shows an experimental setup of the tight packet test.

Figure 3b shows the macroscopic appearance of the galvanized steel after 20 days in a humidotherm chamber for plates rinsed with water without additive.

Figure 3c shows the macroscopic appearance of the galvanized steel after 20 days in the humidotherm chamber for plates rinsed with water with 5% of solution 2 (the black areas correspond to the corroded areas).

Figure 4 shows the voltammetric curves (i = f (E) on AA2214 in NaCl (3.5 g L ^-1 ).

In the remainder of the present description, the examples (solution 1 to solution 5) of concentrated solution are given as illustrations but can not be limiting of the invention.

Solution 6 is given for comparison and does not fall within the scope of the invention.

Table 1: Possible compositions for 1000 g of solution.

The three formulations 1 to 3 lead to concentrated liquid solutions, clear and completely dilutable in water, without any other addition.

The 4 ^th solution (with hydrogen peroxide) is discussed in Example 2.

Example 1

This example is intended to illustrate the protection against corrosion provided by the inhibiting formulation created according to the invention in industrial water circuits according to ASTM D1384. It is obvious that these tests could have been carried out according to other standards and therefore it must not be considered that the invention is limited to protection within the scope of this standard.

According to this standard, corrosive water called "ASTM" contains 165 mg / l of sodium chloride, 138 mg / l of sodium bicarbonate and 148 mg / of sodium sulfate.

Test solutions are prepared by diluting inhibiting solutions (solution 1 to 3 in Table 1) in ASTM water; no agent nor basic nor acid is added to the mixtures, all of which have a so-called "natural" pH between 8 and 8.5.

The Ecor corrosion potential and the Rp polarization resistance of XC38 steel

(Designations well known to those skilled in the art) are measured for 24 hours immersion in ASTM water with or without 1 to 5% of solutions 1, 2 and 3.

The corrosion potential makes it possible to evaluate the enninozation of the material in contact with the water added with inhibitors, and the polarization resistance is inversely proportional to the corrosion rate expressed in μηι / year.

These results (see Figures 1a to 1d) show a significant increase of about 500 mV of the corrosion potential in the presence of solutions 1 to 5 in ASTM water simulating industrial water.

The polarization resistance is increased by a factor of 100 in the presence of the solutions; the corrosion rate of the steel is therefore reduced by a factor of 100 in ASTM water.

The addition of only 1% of one of the solutions is enough to be effective; however, the use of a higher concentration (5%) allows a faster protection of the steel and slightly more effective, beyond 5% we obtain an asymptote because the anti-corrosion gain is low from this value and, moreover, the economic interest is lost.

It is interesting to observe that the nature of the type of neutralizer (organic or inorganic acid) has little or no influence on the corrosion resistance of the film formed by the formulation according to the invention. Indeed, the addition of sulfuric acid or short chain carbon carboxylic acids such as heptatonic or undecylenic acid does not deteriorate or significantly improve the anticorrosion properties of the formulation.

In comparison with the comparative solution 5 used at 5%, containing only potassium heptanoate, it is possible to note that potassium heptanoate used at this low concentration (about 10 ³ mol / l in solution 6 to 5%) does not provide sufficient corrosion protection with a polarization resistance between 50 to 100 ka.cm ²

Likewise, in addition to its bactericidal properties, the use of benzoic acid in solution 3 makes it possible to form a more noble protective film on the surface of the metal and to improve its protection.

From these results, it appears that the formulation 'according to the invention makes it possible to very satisfactorily protect industrial water circuits in steel and zinc-coated steel.

Without wishing to be bound by any theory, the applicant believes that the inhibitory action of solutions 1 to 3 is related to the formation of a crystallized film of metal soap on the surface of metals. In our case, the formation in a totally aqueous medium of long carbon chain metal soaps ("C14 to C22") allows a very high stability and hydrophobicity of the surface.

The Applicant believes that the good results obtained with castor oil are surely due to the stability of this oil during the rise in cooking temperature and resistance to attack by potash.

With linseed oil, for example, the Applicant has observed that the oil "caramelizes" in minutes and that it is impossible to cook.

With all the other oils tested, the Applicant has failed to obtain a stable solution as obtained with castor oil: the preparation is en masse or gelled, making its use very poorly compliant with industrial requirements but having a anti-corrosion power according to the invention (see Table 3).

These failures with oils, a priori promising, and the selection of castor oil reinforce the surprising nature of the invention.

Example 2

This example is intended to illustrate the protection against corrosion provided by the inhibitory formulation created according to the invention under temporary protection conditions of steel metal products according to DIN 51 360. It is obvious that these tests could have been other standards and therefore the invention should not be considered to be limited to protection under this

This standard is intended to simulate the application of inhibitory formula on steel parts, and then the natural drying in the open air of this formula.

The principle of the test is to soak iron chips on a filter paper placed in a petri dish; after two hours the paper is removed, rinsed and dried. The degree of corrosion is evaluated in relation to any traces of rust on the filter paper using standard references.

The corrosive solution to which solutions 1 to 3 will be mixed is composed of 3.58 mmol / L CaCl ₂ , 6H ₂ O and 3.58 mmol / L MgSO ₄ , 7H ₂ O. Solution Dilution in the solution Degree of corrosive concentrated rust (in mass)

Without additive 4

Solution 1 5% 2

Solution 5 5% 2

Solution 4 5% 0

Table 2

On reading Table 2 above and Figures 2a to 2c corresponding, it appears that the formulation of the invention can respond very satisfactorily to the resistance against atmospheric corrosion in cases of air drying free very random.

Example 3

This example is intended to demonstrate that the treatment of a zinc-coated steel sheet with the aid of the solution 4 according to the invention protects the sheet against the risks of corrosion, in particular "punctures" inside the sheet. stacks due to moisture retention phenomenon.

To apply the treatment to the samples, immersion, spraying or coating may be used; thanks in general to the use of an ink roller in contact with the metal.

After application of the solution, the test pieces are drained and then stacked 5 by

5 with a constant predetermined force according to the arrangement shown in FIG.

4a, and placed in a climatic chamber corresponding to DIN 50017, which simulates the storage conditions of metal parts.

This tight packing test (packing test) recreates the containment that exists when stacking metal parts during transport or storage.

After a first drying cycle of 8h at 40 ° C, the stack undergoes cycles (one cycle = 24 hours) in the humidifier enclosure, described below:

- 8h at 40 ° C and 95-100% relative humidity,

-16h at 20 ° C and 75% relative humidity.

After disassembly of the stack, the sheet metal specimens are dried and any traces of corrosion are noted visually. The result of the test is obtained by raising the number of successive cycles before the corrosion traces appear within the stack. When the number of cycles recorded is greater than 20, the resistance against corrosion in stacking is in line with expectations.

According to FIGS. 3b and 3c, the plates rinsed with water added with 5% of solution 2 only show very slight tarnish after 2 days of stacking. under pronounced differential aeration conditions between the inside and the outside of the stack.

The application of the formulations according to the invention thus makes it possible to very effectively protect against corrosion appearing in stacks of metal parts because of moisture retention.

Indeed, the treatment of metals according to the invention application can greatly reduce the wettability of the metal surfaces. The wettability of a material is measured by the contact angle, Θ, only with a drop of water (Figure 5).

Figure 5 shows the definition of the contact angle Θ formed by a drop of water placed on a surface.

When this angle is greater than 90 ° (generally between 90 ° and 120 °), the surface is hydrophobic (the contact surface between water and the material is small) and when it is less than 90 °, the surface is hydrophilic (the contact surface between water and the material is high).

As shown by the results in Table 3, the contact angle of untreated zinc after corrosion is very low due to the presence of atmospheric zinc corrosion products, mainly composed of hydrozincite Zn ₅ (CO ₃ ) 2 (OH) 8, very hydrophilic.

Table 3: Contact angle measured after 6 climatic chamber corrosion cycles (6 days)

After corrosion, the treated surface of zinc still has a very hydrophobic character, because of a nanometric layer of size crystals of the order of 100 nm. This layer of entangled and insoluble crystals makes it possible to trap air and maintain long-lasting hydrophobic properties on the surface of the metal. This hydrophobic effect or "lotus effect" of the treated metal surface is maintained after several days in a corrosive condition.

Example 4

This example serves the same purpose as Example 1 applied to aluminum alloys, in particular Al-Cu alloys. Indeed, in industrial water circuits, these alloys have a significant sensitivity to localized corrosion phenomena ("pitting") due to the presence of copper-rich particles within them.

The voltammetric curves, shown in FIG. 4 (i = f (E) on AA2214 in NaCl 3.5 g L ^"1 ), reveal a significant increase in the corrosion potential (+300 mV) of the AA2214 alloy in presence of 5% of solution 2. With 5%, this ennoblement is accompanied by a reduction in the corrosion rate by a factor of 10, and the formation of a protective layer demonstrated by passivation stage marked by a low current density beyond 0V (about 10 ⁶ A cm ² ). This particular property of the formulation is necessary in the case where the aluminum alloys are in a galvanic coupling condition with noble metals (steel, cuprous alloy) in industrial water circuits.

The 1% assay of solution 2 shows less effective anticorrosion properties than the 5% assay. However, the limited ennoblement and the decrease of the current density between -0.5 V and -0.1 V with this assay may be sufficient in practice in the case of industrial waters with little corrosive effect.

Table No. 4 below lists the tests carried out by the Applicant with different oils tested. These tests were carried out according to the method of the invention.

*

Table 4

It can be seen in the table above that only castor oil makes it possible to obtain a saponification giving a product in concentrated solution, very stable, and moreover limpid which makes this product remarkably adapted to industrial applications of all kinds.

On the other hand, it is seen in the same table that the other oils tested according to the same process according to the invention lead to products that are judged to be incorrect because they form a kind of thicker paste which makes the industrial application problematic, including included in the stability, so that these oils are absolutely not preferred according to the invention.

Nevertheless, these pastes have substantially the same anti-corrosion power on metals and may optionally be used in certain domestic applications, or certain industrial applications where the quality is the properties obtained with castor oil would not be required.

These last industrial applications are marginal but nevertheless conceivable.

Example 5

This example is intended to illustrate the anticorrosive effectiveness of the formulations according to the invention in the case of previously oxidized metals. Indeed, the formulations can be used as basic electrolyte in the so-called clogging process of anodized aluminum.

The tests were carried out on an alloy known to be difficult to protect, the alloy of composition AA7050.

A range of conventional surface treatment has been applied to this alloy comprising the 3 main phases: chemical etching, anodizing, clogging. The following sequence was used:

1 / Chemical pickling (Novaclean AL85 - Henkel),

21 Static rinsing,

3 / Rinsing current in deionized water,

4 / Anodization with conventional electrolyte or electrolyte according to the invention, 4 / current flushing in deionized water,

5 / Clogging with a commercial solution (Anoseal 1000 - Henkel) or a formulation according to the invention

6 / Rinsing current in deionized water

The conditions are detailed in Table 5.

The corrosion tests were carried out in a salt spray chamber according to the ISO9227 standard. corrosion resistance IS09227 (No.

1 / Chemical pickling 2 / Anodizing 3 / Sealing Thickness of R

protective layer of stings / dm2)

Electrolyte Conditions T Electrolyte Conditions T Electrolyte Conditions T (P) after 48h after 500h after 1000η

Novaclean AL85 15V 10min

4min 45'C H2S04200 g / 1 17-19'C Not clogged 7> 20> 20> 20 (Henkel) 21V 15min

Novaclean AL85 15V 10min Anoseal 1000

4min 4S'C H2S04200 g / 1 17-19'C 30 '95' C 7 0 2 5 (Henkel) 21V 15min (Henkel)

Novaclean AL85 12V 15min

4min 45 ° C H2S04200 g 1 17-19'C Solution2 at 30% 30 min 80 * C 7 0 0 0 (Henkel) 18V 12min

Table N ° 5: Treatment conditions and corrosion resistance result

according to IS09227

On the 7050 alloy, which is very sensitive to pitting, the results in Table 5 show that an oxide layer formed by anodizing without clogging is not sufficient to protect against corrosion, since 20 pits of corrosion appear from the beginning. hours of exposure to salt spray.

The conventional sealing process with a commercial solution based on nickel salts (Anoseal 1000 - Henkel) makes it possible to withstand 400 to 500 hours of exposure in salt spray. Although widely used, this solution is barely sufficient to meet the specifications required for certain applications, particularly aeronautical applications.

In addition, the electrolyte Anoseal 1000 poses problems of hydiene and safety due to the presence of Ni ²⁺ in the solution.

The formulation according to the invention diluted to 30% and used at 80 ° C as a clogging electrolyte significantly improves the corrosion resistance of the anodized layers on this type of alloy. It is possible to reach 1000 hours of salt spray exposure without pitting according to ISO 9227.

The invention also covers all the embodiments and all the applications which will be directly accessible to the person skilled in the art upon reading the present application, and of his own knowledge.

Claims

claims

1- anticorrosion composition for "metals" characterized in that it consists or comprises at least one saponification product of at least one vegetable oil, or mixture of vegetable oils, the vegetable oil or oils comprising "C14" chains - C22 ".

2- Composition according to claim 1, characterized in that the vegetable oil used is castor oil.

3- Process for manufacturing in a single reactor ("one pot" process) a saponified composition of vegetable oil containing up to 30% by weight of fatty substances (in other words product resulting from saponification) for the purpose of inhibiting corrosion for metals, characterized in that it comprises the following steps: a) During a first phase, a quantity of vegetable oil (between 15 and 35% of the final mixture) is mixed with a solution of hydroxide of potassium (between 5 and 20% of the final mixture);

the mixture is heated under constant agitation at a temperature of between 70 ° C. and 99.9 ° C. (atmospheric pressure boiling limit) at atmospheric pressure for 15 to 30 minutes;

b) a quantity of water is prepared representing between 50 and 80% by weight of the final mixture (preferably between 45 and 80% of the final mixture) heated between 70 ° C and 99.9 ° C (pressure boiling limit under pressure atmospheric pressure) and then performs steps c and d.

c) the hot water prepared under b) is then incorporated into the composition obtained in step a) with constant stirring taking care not to form bubbles;

d) the new mixture is then cooled to the temperature of use.

4. Process according to claim 3, characterized in that the process is carried out in a single reactor or "one-pot".

5. Process according to claim 3 or 4, characterized in that during step a) the mixture is preferably brought to a temperature between 85 ° C and 95 ° C at atmospheric pressure.

6. Process according to any one of claims 3 to 5, characterized in that, in order to modify the pH of the solution obtained is added at the end of step d) as a neutralizer, an acidic compound such as an acid organic or mineral or borax.

7- Process according to claim 6 characterized in that the benzoic acid is used. 8- Process according to any one of claims 3 to 7, characterized in that it further comprises the addition of oxidizing agents or accelerators such as salts of nitrites / nitrates, persulfates, perborates, percarbonates or hydrogen peroxide, preferably the addition of 1 to 20% by weight of hydrogen peroxide for its non-toxic nature and harmless to the environment.

9- Process according to any one of claims 3 to 8, characterized in that it further comprises the use of

an antifoaming agent, and / or

additional bactericidal / fungicidal compounds,

one or more acid-base compounds, allowing a better stability in pH (buffer solution) (eg addition of 0.01 mol / l Na2B4O7,10H ₂ O).

10- Product or composition for protecting against corrosion of "metals" sensitive to atmospheric oxidation, characterized in that they are prepared according to the process according to any one of Claims 3 to 9.

11- Product or composition according to claim 10, characterized in that it contains metal soaps long carboxylate chain "C14 - C22", especially C18.

12- Product or composition according to claim 10 or 11, characterized in that it comprises 0.2 to 5% by weight of at least one triazole derivative and / or 0.2 to 20% by weight of an oxidizing compound or accelerator.

13. Product or composition according to any one of claims 10 to 12, characterized in that the triazole derivative is selected from the group consisting of benzotriazoles, tolyltriazoles and alkyltriazoles.

14- Product or composition according to any one of claims 10 to 13, characterized in that the oxidizing derivative or accelerator is selected from the group consisting of nitrite salts / nitrates, persulfates, perborates, percarbonates or salts. 'oxygenated water.

15- A product or composition according to any one of claims 10 to 14, characterized in that the composition contains from 0.002 to 2% by weight of wetting agent selected from the group consisting of anionic surfactants such as alkyl sulphates and nonionic surfactants such as ethoxylated compounds of the fatty alcohol type and alkylphenols.

16- A method of depositing the product or the composition according to any one of claims 1 and 2, and 10 to 14 in that it consists:

to dilute said composition between 0.2 and 30% by weight in water,

bringing the solution thus formed into contact with the metal surface during residence times ranging from 10 seconds to 24 hours,

draining said solution and then drying said surface in free air or under a possibly heated air stream.

17- Uses of the product or composition according to any one of claims 1 and 2, and 10 to 14, in the form of non-oily dry film to cover "metals", selected from the group formed by Iron and its alloys; Copper and its alloys; Aluminum and its alloys, Zinc and its alloys; Lead and its alloys; tin and its alloys; including all of these partly corroded metals.