EP0996769B1 - Compostion for temporarily protecting metal parts against corrosion, preparation and application methods and metal parts obtained from said compostion - Google Patents

Abstract

The invention concerns a composition useful for providing temporary protection against corrosion to metal surfaces comprising an oil-in-water emulsion characterised in that said emulsion contains in its aqueous phase at least a compound of general formula (I) in which the groups R, R1 and R2 represent independently of one another a hydrogen atom, a C1-C20 alkyl group, a C1-C20 halogenoalkyl group with the halogen being chlorine, bromine, iodine or fluorine, a C3-C6 cycloalkyl group, a carboxylic function or a C1-C6 carboxyalkyl group; n is a whole number varying from 1 to 3; and X represents an oxygen or sulphur atom in the form of one of its soluble salts. The invention also concerns a method for preparing said composition, its method of application to the surface of metal part and the resulting part.

Description

The subject of the present invention is a composition useful for temporarily protect metal parts from corrosion, a process for preparation of said composition and the metal parts coated with a dry film deriving from it

The problem of temporary protection of metallic surfaces and more particularly metal sheets against atmospheric corrosion is a constant concern of industrialists Multiple possibilities therefore exist already to give the surface of the sheet a temporary mode of protection by bold films. especially based on traditional protective oils.

However, the increase in user requirement criteria has leads steelmakers to come up with increasingly sophisticated solutions account for a wide variety of factors (appearance, aptitude for surface treatment, cleanliness premises, security, toxicology ...) These imperatives have thus been partly satisfied by developing a non-greasy coating and its method of application, the virtues give the sheet thus treated temporary protection properties against corrosion of around two months (FR 92 08 037)

However, there remains a request from users to coatings with even better corrosion resistance, without prejudice of course, subsequent use properties and in particular endowed prolonged corrosion resistance with preferably resistance to corrosion greater than three months

The object of the present invention is precisely to propose a new coating meeting these requirements

A first approach consists in incorporating into the coatings a based on temporary protection oil formulations, one or more inhibitors corrosion.

• des composés aminés de type alcoolamines,
• des dérivés de sulfonates comme leurs sels de baryum ou de sodium ou des alkylbenzènes sulfonates et
• des acides de type linoléique...

Conventionally, the corrosion inhibitors present in protective oils are chosen from

• amino compounds of the alcoholamine type,
• sulfonate derivatives such as their barium or sodium salts or alkylbenzene sulfonates and
• linoleic acids ...

Unfortunately, the gain in corrosion resistance obtained with these conventional inhibitors, is not satisfactory.

Consequently, there remains to this day a need for a mode of temporary protection for metal parts having an improvement significant in terms of corrosion resistance (more than three months). a dry appearance, aptitude for surface treatment with or without preparation and in addition, complies with toxicology rules (absence of barium, metal salts heavy ..)

This is how the plaintiff has shown that the incorporation within the oil-in-water emulsion, a heterocyclic thioether of acids saturated carboxylic acids, as a corrosion inhibitor, would respond precisely and satisfactorily to all of these requirements.

EP 129506 proposes the use of heterocyclic thioether of acids carboxylates related to those of the invention, as a corrosion inhibitor. However, these compounds are introduced directly into the oily phase of the corresponding emulsions.

   dans laquelle les groupements R, R₁ et R₂ représentent indépendamment l'un de l'autre un atome d'hydrogène, un groupement alkyle en C₁ à C₂₀, un groupement halogénoalkyle en C₁ ou C₂₀ avec l'halogène pouvant être le fluor, le chlore, le brome ou l'iode, un groupement cycloalkyle en C₃ à C₆, une fonction carboxylique ou un groupement carboxyalkyle en C₂ à C₆,

n est un entier variant de 1 à 3 et

X représente un atome de soufre ou d'oxygène,

sous la forme d'un de ses sels hydrosolubles,

   caractérisée en ce que ladite émulsion est obtenue par émulsification d'une phase aqueuse, dans laquelle a été incorporé au préalable ledit composé de formule générale I, avec une phase huileuse.More particularly, the present invention relates to a composition useful for imparting temporary protection against corrosion to metal surfaces comprising an oil-in-water emulsion containing in its aqueous phase at least one compound of general formula I

in which the groups R, R ₁ and R ₂ represent, independently of one another, a hydrogen atom, a C ₁ to C ₂₀ alkyl group, a C ₁ or C ₂₀ haloalkyl group with the halogen capable of be fluorine, chlorine, bromine or iodine, a C ₃ to C ₆ cycloalkyl group, a carboxylic function or a C ₂ to C ₆ carboxyalkyl group,

n is an integer varying from 1 to 3 and

X represents a sulfur or oxygen atom,

in the form of one of its water-soluble salts,

characterized in that said emulsion is obtained by emulsification of an aqueous phase, in which said compound of general formula I has been incorporated beforehand, with an oily phase.

Preferably, it is a compound of general formula I in which R represents a hydrogen atom and X a sulfur atom.

Unexpectedly, adding an oil-in-water emulsion, of a corrosion inhibitor in accordance with the present invention, gives the coating corresponding, a significantly prolonged corrosion resistance in the time. This improvement is in fact much greater than that equivalent to the superimposition of the respective effects of the emulsion and of said inhibitor, in terms of corrosion resistance. It is advantageously the reflection of a synergy between the two components.

The originality of the claimed composition rests on the incorporation of a compound of general formula I in the aqueous phase and not in the phase lipid of the emulsion, used in the composition claimed. Not water-soluble in nature. this compound is therefore present in the composition in neutralized form with a view to giving it water-solubility satisfactory.

This neutralization of the compound or compounds of formula I. used according to the invention, can be carried out conventionally by a person skilled in the art. She can for example be obtained from ammonia, morpholine, ethanolamine, ethanol or potash. Depending on the reagent used, it may be, if necessary necessary to adjust the pH of the final composition, to a value compatible with the recommended application, i.e. at a value between 8.2 and 9.5 and preferably between 8.5 and 9 This can be easily achieved by adjusting the pH of the final emulsion by an additional addition of neutralizer such as ethanolanine for example

The corrosion inhibitor of general formula I is preferably present in the claimed composition in an amount of 1 to 10 g / l and preferably 1 at 3.5 g / l.

As preferred compounds of general formula I, mention will be made of any particularly the water-soluble salts of benzothiazolylthiosuccinic acids, α- (benzothiazolylthio) stearic acid, lauric α- (benzooxazolylthio), caproic α- (benzothiazolylthio) and α- (benzothiazolylthio) caprylic.

More preferably, it is a water-soluble form of the acid benzothiazolylthiosuccinique (ABTS) and more specifically its ammonium salt or ethanolamine.

As regards the emulsion, it can be defined as comprising in dispersion in water, 3 to 13% by volume of an oily phase comprising from 75 to 90% by volume of at least one oil and from 5 to 10% by volume at least one surfactant If applicable, an additional corrosion inhibitor may be present at a rate of 5 to 15% by volume, in the oily phase.

Preferably, the emulsion comprises, in dispersion in the phase aqueous, between about 3 and 8% and preferably about 6% by volume of a oil.

The oil contained in the oily phase of the emulsion can be consisting of mineral, vegetable or animal oil.

Advantageously, it is a mineral oil and preferably a paraffinic, naphthenic type oil or a mixture thereof.

As mineral oil, preferably used according to the present invention, particular mention will be made of the soluble oil AQUASAFE 21® from CASTROL.

It is preferred to use as surfactant for the oily phase a polyoxyethylene type surfactant.

Advantageously, the corrosion inhibitor used is oily phase, a carboxylic acid, a sodium or barium alkyl sulfonate or an amine and fatty acid salt.

According to a preferred embodiment of the invention, the composition claimed includes a water-soluble salt of the acid as a corrosion inhibitor benzothiazolylthiosuccinique (ABTS), present, at a concentration between 1 and 3.5 g / l and preferably of the order of 2.5 g / l, in the aqueous phase of a 6% emulsion in soluble oil which is preferably AQUASAFE 21® oil from CASTROL. Preferably, it is the ammonium salt of the acid benzothiazolylthiosuccinic present at a concentration of the order of 2.5 g / l.

The present invention also relates to a method of preparation of said composition.

More particularly, this process is characterized in that the one or more compounds of general formula I are incorporated in the form of a solution aqueous at the aqueous phase of the emulsion, prior to its emulsification with the oily phase.

Unexpectedly, the Applicant has indeed noted that the mode of incorporation, of the compound of general formula I into the emulsion, had an incidence significant on the anticorrosion activity of the corresponding composition It is as it turns out to be particularly advantageous to introduce this compound of formula general I in the form of an aqueous emulsion solution. It remains so dispersed in the aqueous phase of the emulsion. It has been observed that the addition of this compound directly within the oily phase of said emulsion significantly affected the anticorrosion behavior of the composition resultant. This effect is more precisely demonstrated in Examples 7 and 9 below.

The present invention also relates to a method of temporary protection against corrosion of metal parts

• appliquer sur une partie au moins de ladite pièce métallique une composition selon l'invention, et
• sécher ladite pièce métallique revêtue jusqu'à obtention d'un film sec

More particularly, this method is characterized in that it comprises the steps consisting in:

• applying a composition according to the invention to at least part of said metal part, and
• dry said coated metal part until a dry film is obtained

According to a preferred mode of the invention, the composition according to the invention is applied to the surface of the metal part so as to saturate its absorption sites for compounds of general formula I and that after heating said composition, in order to obtain a film thereof, no compound of general formula I present in the thickness of the applied film.

The performance of the coating film is indeed clearly improved if the application of the composition claimed on the metal plate to process is carried out so as to saturate its adsorption sites with a compound of general formula I and to prevent the accumulation of this same compound of formula general I in terms of film thickness.

It is therefore desirable to adapt its mode of application so as to optimize this saturation of the adsorption sites on the treated surface, and minimize on the other hand the concentration of compounds of general formula I in the thickness of the emulsion film after drying. The parameters to consider, for this adjustment of the concentration of the composition claimed on the surface of the treated plate are the desired film thickness, the concentration of this composition, in phase oily and in compound of general formula I. It is within the reach of those skilled in the art to make this adjustment by routine operations taking into account these different parameters.

Adjusting the optimal concentration of formula inhibitor general I on the surface of the metal part to be treated can for example be appreciated and performed as follows, after applying and drying on the surface of the exhibits a composition according to the invention, of determined concentration corrosion inhibitor (s) of general formula I. The leaching of the acetone, dip or spray piece. Then, we measure the level of saturation of the adsorption sites on the surface of the treated metal part performing an infrared spectrum of the leached room, using the technique of Fourier infrared transform spectroscopy (IRFT) under grazing incidence at 80 ° The fact that an interfacial film rich in inhibitors of general formula I remains or not at the end of this leaching, as well as the residual thickness of this film. are already indicative of the degree of adsorption of said inhibitor. By comparing with infrared spectra performed on other parts treated with compositions with different concentrations of inhibitor and leached from the same way we can then determine if the adsorption sites on the surface metallic are saturated or not, i.e. if the inhibitor concentration is sufficient in the composition to obtain an effective treatment.

We then check that we have not applied to the part a composition so concentrated in inhibitor that saturation would have been exceeded adsorption sites, to the point that we would find a significant part of the composition inhibitor, in the thickness of the dry film applied to the surface metallic. To this end, we analyze, for example by infrared spectroscopy also, the inhibitor content in the leachate. By comparison with infrared spectra performed on leachate from other parts treated with compositions with different concentrations of inhibitor and leached in the same way, we can then determine if the inhibitor concentration in the composition is too high for effective treatment.

This results in the adjustment of the inhibitor concentration in the composition.

The aqueous composition according to the invention can be clearly understood deposited in the form of a film, on the surface of the metal parts to be protected, by any suitable conventional means such as a roller coating device or similar or by spraying. The part thus treated, then undergoes a drying in order to obtain a dry film, in accordance with the invention

This heating can be, for example, carried out by wearing the part treated at a temperature between 50 and 100 ° C for a varying time between about 20 seconds to 10 minutes.

The present invention also relates to a metal part coated with a dry film for temporary protection against corrosion obtained from the composition claimed and / or in accordance with the claimed processes

Preferably the surface density of dry film on the surface of the part varies between 0.3 and 2 g / m ³ and more preferably is of the order of 0.5 g / m ²

For the purposes of the invention, the term "metal parts" is used. of the hot-rolled medium thickness plates, thin-rolled sheets hot, cold rolled steel sheets as well as various kinds of plates and sheets steel, especially bare steel.

As previously stated, metal parts coated with a dry protective film of composition as defined according to the invention, prove resistant to corrosion and exhibit good drawing and bonding. What is more, the dry films obtained according to the claimed process. show good adhesion properties with respect to natural substrates various, on the surface of which they are likely to be applied to their surface.

Furthermore, the coatings derived from the claimed compositions have satisfactory tribological performances and therefore advantageous stamping level. This is how their characterization in terms of friction shows that they have a reduced coefficient of friction compared to conventional coatings.

The compositions according to the invention can also be applied effectively on metal plates already coated with a dry film, and are found therefore particularly advantageous for treating turns and outer edges of coil already coated with a non-greasy coating or to protect parts pickled metal.

Other advantages of the claimed composition will become apparent from the reading of the examples presented below without implied limitation of the present invention.

figures

• Figure 1 Characterization of the optimal concentration of inhibitor of general formula I.
• figure 2 Characterization in impedance of films according to the invention and witness films,
• Figure 3 Friction characterization of a film according to the invention and witness films,
• figure 4 Characterization of the adsorption capacity of a corrosion inhibitor of general formula I, on the surface of a metal part.
• Figures 5 and 6 Characterization of the adsorption capacity of various inhibitors including ABTS.

I - MATERIAL AND METHOD A) Material A 1- Corrosion inhibitors tested

1) Benzothiazolylthiosuccinic acid according to the invention, marketed by CIBA under the name of IRGACOR 252. The ABTS inhibitor is dissolved in an oily emulsion after neutralization with ammonia or ethanolamine. For example, to neutralize and therefore dissolve 1 g of inhibitor in a liter of water, you need at least

• 2 ml of ammonia, or
• 0.2 ml of ethanolamine. These quantities of neutralizer can then be increased (by a few tenths of ml) in order to obtain a final pH (of the emulsion) of between 8.2 and 9.5

2) Irgacor L184, and Irgamet 42 from CIBA.

• The Irgacor L 184

It is an amine salt and polycarboxylic acid, of general formula as follows:

It is generally used with Irgamet 42 also soluble in water and of general formula as follows

The proportion is 1 volume of Irgamet 42 for 19 volumes of Irgacor L184 (cf. compositions 4 and 5 of Table I below)

3) RC 305® marketed by CRODA. It is an aqueous mixture of alcoholamines and amine borates containing 70% water.

4) PX 2881® marketed by ELF It consists of an aqueous mixture of sodium heptanoate and heptonoic acid with perborate.

10-25 % de sels d'aminés tert. de l'acide (2-benzothiazolylthio) succinique C₁₂-C₁₄

+ 10-25 % de sels de monoéthanolamines phosphatées tridécylalcool éthoxyle

+ 10-25 % de sels de zinc d'acides gras ramifiés (C₆-C₁₉)

+ < 2,5 % de sels de zinc d'aide naphténique

+ 10-25 % benzoate de morpholine

Ces inhibiteurs 1 à 5 sont employés pour additiver une émulsion composée d'une huile minérale soluble et d'eau.5) SER AD FA 379 marketed by SERVO HULS group This is a mixture of several inhibitors, offered as a paint additive Its composition is as follows

10-25% tertiary amine salts. (2-benzothiazolylthio) succinic acid C ₁₂ -C ₁₄

+ 10-25% of monoethanolamine phosphate salts tridecyl ethoxyl alcohol

+ 10-25% zinc salts of branched fatty acids (C ₆ -C ₁₉ )

+ <2.5% zinc salts of naphthenic aid

+ 10-25% morpholine benzoate

These inhibitors 1 to 5 are used to additivate an emulsion composed of a soluble mineral oil and water.

A. 2 - Emulsion

The mineral oil used is CASTROL soluble oil AQUASAFE 21®

It is composed of 80 to 95% of a mineral base (naphthenic and paraffinic). Surfactants are incorporated into this product to make it emulsifiable in water (anionic surfactant, sodium alkylsulfonates).

This soluble oil is diluted to 6% in demineralized water and the pH of the emulsion thus obtained is 9.2

A. 3 - Formulations tested

Their compositions were in Table I below Composition Typical concentration 1 (soluble oil) Typical concentration 2 (inhibitor (s)) -1-
CASTROL AQUASAFE 21 emulsion (soluble oil only) 6% 0 (60 g / l) -2-
(ABTS) (inhibitor only) 0 aqueous solution 30 g / l -3-
composition 1 + composition 2 6% 2.5 g / l (60 g / l) -4-
IrgacorL184 + Irgamet 42 0 30 g / l (L 184) and 1.5 g / l (142) -5-
composition 1 + composition 4 6% 30 g / l (L 184) and 1.5 g / l (142) (60 g / l) -6-
composition 1 + PX2881 6% 15 ml / l (60g / l) -7-
composition 1 + PX2881 6% 5 ml / l (60g / l) -8-
composition 1 + RC305 6% 15 ml / l (60 g / l) -9
composition 1 + RC305 6% 5 ml / l (60 g / l)

B) Methods. B 1- Electrochemical impedance measurement - Transfer resistance

The performance of the different compositions tested is assessed by applying them to pickled steel specimens, polished with G600 paper, in proportions such that the final grammage deposited on specimens is of the order of 500 mg / m ² (0.5 µm) . The test piece is then immersed in an electrolyte composed of demineralized water, of 1% by weight of sodium chloride (NaCl). The steel test piece is kept 30 minutes in the electrolyte in order to stabilize its electrochemical potential. After 30 min, using a potentiostat, a frequency analyzer, a reference electrode and a counter electrode, a sinusoidal potential disturbance (in mV) is imposed on the test piece. different decreasing frequencies and we measure "response intensity" (in µA / cm ² )

We can thus obtain impedances (Z = U / l for the different frequencies and draw impedance diagrams. From these diagrams we can deduce a transfer resistance (ohm.cm ² ) which can be assimilated to a " corrosion resistance"

Experimental parameters

• Reference electrode saturated calomel electrode
• Counter electrode platinum electrode
• 7 cm ² steel test tube working electrode
• Potentiostat potentiostat EGG 273®
• Schiumberger 1255® frequency analyzer
• Sinusoidal disturbance ± 5 mV amplitude
• Potential corrosion test
• Frequencies from 100,000 Hz to 0.2 Hz

B 2 - Validation by "FKW" humidotherm test (standard DIN 500l7).

To do this, steel samples, coated with the various compositions to be tested, are suspended in an enclosure whose cycle is as follows 1 cycle = - 8 hours at 40 ° C and 100% humidity - 16 hours at 20 ° C and 75% humidity

The number of cycles before corrosion appears is thus noted. The thickness of the films applied is 0.5 g / m ² on average (0.5 μm). Without contrary indications, the composition is always composed of Castrol AQUASAFE soluble oil. 21, diluted to 6% in demineralized water

B 3 - tests hall EB 1 and hall of finishing

• halle des finissages halle dont l'atmosphère est assez peu sévère (portes fermées).
• halle EB 1 halle très sévère car les éprouvettes sont exposées prés des ouvertures de cette halle et sont donc soumises à une forte humidité par temps de pluie, aux gaz d'échappement des camions et aux poussières de l'aciérie

The test pieces are exposed to the atmosphere of 2 storage halls

• hall of finishing halls whose atmosphere is not very severe (doors closed).
• hall EB 1 very severe hall because the test pieces are exposed near the openings of this hall and are therefore subject to high humidity in rainy weather, truck exhaust gases and dust from the steelworks

In both cases, note the number of days before the onset of corrosion

EXAMPLE 1 Determination of the optimal inhibitor concentration on corrosion resistance.

ABTS inhibitor, neutralized with ethanolamine, is introduced at concentrations varying between 0.5 and 20 g / l in the aqueous phase, in a composition according to the invention comprising an aqueous emulsion based on 6% of CASTROL AQUASAFE 21 The corrosion resistance of the different corresponding compositions are determined by FKW humidifier according to the protocol described in material and method The results obtained are represented on the graph of figure 1

Optimal resistance is observed with the composition comprising 2.5 g / l of ABTS inhibitor in neutralized form

EXAMPLE 2 Estimation of corrosion resistance after atmospheric exposure.

This estimate is made with a composition according to the invention comprising a ABTS concentration equal to 2.5 g / l (COMPOSITION 3) and with regard to control compositions 1, 2 and 4, identified more precisely in the chapter Materials and methods.

These compositions undergo the EB hall and finishing hall tests whose protocols are explained in Materials and Methods.

The results observed with each of the compositions are presented in Table II below. Composition Number of days before corrosion appears (hall EB1) Number of days before corrosion appears (finishing hall) 1 15 to 25 days 66 days 2 2 to 6 days 15 days 3 30 to 65 days 110 days 4 3 days / 5 10 to 20 days /

It is noted that only the composition according to the invention, that is to say the composition 3 comprising an ABTS salt in an aqueous emulsion, present resistance significantly extended over time What is more, the increase in resistance observed is clearly greater than that resulting from superimposition of the resistances induced respectively by the emulsion and by the ABTS. Advantageously, we are seeing a synergy of their effects respective

EXAMPLE 3 Resistance estimation according to a transport test

This test is also carried out on compositions 1,2, 3 and 4, identified more specifically in the Materials and Methods chapter

This test consists of stacking previously coated test pieces by the solutions to be tested. The batteries are kept tight to simulate the turns contiguous with a steel coil or the stacked sheets of a bundle of sheets.

The stacked stack of test pieces ("tight packet") is then introduced into a climatic chamber programmed to alternate 32 hr cycles ("transport cycle").

• 10 h à 40°C et 95 % de RH
• 4 h à 20°C et 80 % de RH
• 10 h à -5°C et 0 % de RH
• 8 h à 30°C et 85 % de RH

Details of the transport cycle (1 cycle = 32 hours)

• 10 h at 40 ° C and 95% RH
• 4 h at 20 ° C and 80% RH
• 10 h at -5 ° C and 0% RH
• 8 h at 30 ° C and 85% RH

• chaque cas de figure est représenté par 4 éprouvettes,

In the "transport cycle" configuration, the tests are carried out on tight packets under the following conditions:

• each case is represented by 4 test tubes,

observations are made every three cycles packets are open and we observe the state of the interfaces.

The results are shown in Table III below. compositions Number of cycles before corrosion appears 1 <6 cycles 2 <6 cycles 3 > 19 cycles 4 <6 cycles 5 <6 cycles

Only the metal part coated with a composition according to the invention i.e. composition 3 exhibits corrosion resistance significantly improved This increase also reflects a synergy between the emulsion and the ABTS salt.

EXAMPLE 4 Validation for humidotherm test

It is carried out according to the protocol described in the Materials chapter and Methods, on compositions 1 to 9 defined in this same chapter

Except for compositions 2 and 4, based on an aqueous solution containing ABTS and an Irgacor L184 / Irgamet 42 mixture respectively, tested compositions are always composed of Castrol AQUASAFE soluble oil 21, diluted to 6% in demineralized water (composition 1) and added with different inhibitors (compositions 3 and 5 to 9)

The results presented in Table IV below are observed compositions Number of cycles before corrosion appears 1 12 cycles 2 1 cycles 3 > 22 cycles 4 1 cycle 5 <12 cycles 6 12 cycles 7 8 cycles 8 12 cycles 9 15 cycles

By this test, we confirm that the different control inhibitors tests do not have the effectiveness of the ABTS product and the existence of synergy only between an inhibitor of general formula I and an AQUASAFE 21 emulsion

EXAMPLE 5 Estimation of the corrosion resistance through the transfer resistance.

This test was carried out by establishing the electrochemical impedance diagrams of compositions 1 and 3 identified in the Materials and Methods chapter, tested, according to the protocol described in this same chapter. The results are shown in Table V below. compositions Transfer resistors in kΩ.cm ² 1 10 to 20 kΩ.cm ² 3 60 to 120 kΩ.cm ²

EXAMPLE 6 Effect of ABTS salt concentration on the interfacial film on the corrosion resistance.

2) émulsion seule

3) émulsion + 5 % solution aqueuse d'ABTS sans séchage.

4) émulsion + 5 % solution aqueuse d'ABTS puis séchage à 60°C pour obtenir un film de 650 mg/m²

5) émulsion + 3,5 % solution aqueuse d'ABTS puis séchage à 60°C pour obtenir un film de 250 mg/m²

6) émulsion + 3,5 % solution aqueuse d'ABTS puis séchage à 60°C pour obtenir un film de 700 mg/m²

According to the protocol described in the Materials and Methods chapter, impedance curves have been established for metal parts coated with the following compositions.

2) emulsion only

3) emulsion + 5% aqueous solution of ABTS without drying.

4) emulsion + 5% aqueous ABTS solution then drying at 60 ° C to obtain a film of 650 mg / m ²

5) emulsion + 3.5% aqueous ABTS solution then drying at 60 ° C to obtain a film of 250 mg / m ²

6) emulsion + 3.5% aqueous ABTS solution then drying at 60 ° C to obtain a film of 700 mg / m ²

In emulsions 3 to 6, ABTS is present in a form neutralized with ammonia. The drying of emulsions 4 to 6 therefore leads to a evaporation of ammonia.

The results are presented in figure 2 with the real part of the impedance expressed on the abscissa and the imaginary part of the impedance in orderly

Examination of these curves shows that at film thickness equivalent, better behavior of a film obtained with 3.5% is observed. ABTS (composition 4) than 5% in ABTS (composition 6). An excess of ABTS at level of the resulting film therefore has an unfavorable effect.

Furthermore, it can be noted that the completion of a step of drying (composition 4) gives an advantageous behavior to the film corresponding to a film which has not undergone drying (composition 3) This effect is in fact linked to the implementation of ammonia-neutralized ABTS

EXAMPLE 7: Effect of the preparation protocol on the effectiveness of a composition according to the invention

The performances of a composition prepared according to the process of the invention and of a composition prepared by addition of ABTS in soluble oil, prior to its emulsion, are compared in terms of resistance to corrosion. The results are presented in Table VI below.

Total resistances are determined by impedance electrochemical. performed according to the protocol described in the Hardware chapter and Previous method

From these results it appears that the mode of adding ABTS to within the composition according to the invention, has a non-negligible effect

In an equal amount, if it is dissolved in soluble oil, before setting in emulsion, performance is significantly reduced in terms of corrosion resistance.

EXAMPLE 8 Friction characterization of the proposed compositions.

The single-pass friction tests are carried out in plane-plane friction, at variable transverse pressure from 200 to 2,000 daN with high-speed steel tools, with an area of 1 cm ^2. The speed of movement is 2 mm / s.

The test pieces are cut from hot pickled sheets. grade BS2, in thickness of 2 mm.

• Composition A une huile de protection utilisée sur les tôles comme protection contre la corrosion (QUAKER 8021) déposée à raison de 2 g/m²
• Composition B l'huile soluble AQUASAFE 21 à 6 % dans l'eau, déposée à raison de 500 mg/m²
• Composition C Composition B additivée de l'inhibiteur organique ABTS sous forme de sel, (pH de la solution compris entre 7,2 et 8,5) déposée à raison de 500 mg/m²
• Composition D identique à la composition C, dont le pH est stabilisé entre 8,5 et 9 par l'ajout d'éthanolamine, déposée à raison de 500 mg/m²

The performances of two compositions according to the invention are compared with two control compositions whose behaviors in tribology appear in FIG. 3.

• Composition Has a protective oil used on the sheets as corrosion protection (QUAKER 8021) deposited at a rate of 2 g / m ²
• Composition B AQUASAFE 21 soluble oil at 6% in water, deposited at a rate of 500 mg / m ²
• Composition C Composition B supplemented with the organic inhibitor ABTS in salt form (pH of the solution between 7.2 and 8.5) deposited at a rate of 500 mg / m ²
• Composition D identical to composition C, the pH of which is stabilized between 8.5 and 9 by the addition of ethanolamine, deposited at the rate of 500 mg / m ²

The friction curves improve with compositions C and D The results obtained are better than with a protective oil, having stamping properties (composition A)

EXAMPLE 9 Characterization of the adsorption capacity of the ABTS inhibitor

According to a first method, wettability measurements are carried out of two compositions, a composition based on an AQUASAFE 21 emulsion (WITNESS) and a composition based on an additive AQUASAFE 21 emulsion by ABTS (ABTS) at a concentration of 2.5 g / l, in the form of its salt neutralized and at pH around 8.5 to 9

The test consists in depositing a drop of each of the emulsions on a steel test piece and to follow the evolution of the contact angle of the drop (follow-up sprawl)

The graph shown in Figure 4 shows that a drop of emulsion AQUASAFE 21 additivated by ABTS (ABTS) spreads much faster on steel than a drop of classic AQUASAFE 21 emulsion (WITNESS). These results show that ABTS fulfills the role of a spreading agent. It helps to make a more homogeneous, more covering film.

This adsorption power is also appreciated by the infrared spectrum. according to the following protocol and with the compositions defined below in the table VII

In all cases, the compositions tested comprise an emulsion having an oily base concentration of AQUASAFE 21 of 5% Composition Concentration in ABTS ABTS dissolved in: pH of emulsions AT 0.25% oil 9.7 B 0.125% oil 10.1 VS 0.25% emulsion 9 D 0.75% emulsion 8.9 E 3.75% emulsion 10.2

• les films A et B sont totalement éliminés par la lixiviation On peut donc en déduire que l'inhibiteur est faiblement adsorbé dans le cas de ces compositions ,
• après lixiviation des films C, D et E, il subsiste un film interfacial dont l'épaisseur augmente avec la concentration initiale en inhibiteur De même la teneur en inhibiteur dans ces films interfaciaux résiduels (huile de base - inhibiteur) augmente avec la concentration finale

Emulsions A, B, C, D and E are applied to polished test pieces. In order to study the film-steel interface, the infrared spectrum is produced on the test tube after leaching with acetone (grazing IRFT spectra, 80 ° incidence). It is thus observed that

• films A and B are completely eliminated by leaching. It can therefore be deduced therefrom that the inhibitor is weakly adsorbed in the case of these compositions,
• after leaching of films C, D and E, there remains an interfacial film whose thickness increases with the initial concentration of inhibitor Similarly the inhibitor content in these residual interfacial films (base oil - inhibitor) increases with the final concentration

This test therefore confirms that it is preferable to add the inhibitor ABTS with SOLCLEAN emulsion and not in base oil before emulsification (composition C with respect to A). Thus, the inhibitor can adsorb strongly on steel and play its role optimally. These spectra are in perfect coherence with corrosion tests.

From their examination, it also appears that the performances are less good when ABTS is found in the thickness of the oil film dried, that is to say in the leaching effluents. This is particularly the case with composition E which includes 3.75% ABTS.

EXAMPLE 10 Comparison of adsorption capacity or ABTS compared to others water-soluble or water-soluble corrosion inhibitors.

The effect of the ABTS concentration neutralized with ethanolamine in aqueous solution, applied to bare sheet metal, is compared with that of the inhibitors, RC 305, PX 2881 and SER AD FA 379, identified in the MATERIAL and METHOD chapter. This effect is assessed by electrochemical impedance measurements according to the protocol described above. The various inhibitors are tested between 0.5 and 20 g / l and the transfer resistances ("corrosion resistance") obtained are shown on the graphs of FIGS. 5 and 6 It appears that only the ABTS inhibitor has an optimal adsorption peak on the surface of the bare sheet, with the latter centered on 2.5 g / l. As for the other inhibitors tested, they reveal an increasing effectiveness with the concentration but still lower than that of ABTS (30,000 Ω cm ² at 2.5 g / l). With regard to the inhibitor SER AD FA 379, the content of ABTS in this inhibitor is too low to observe results in accordance with the invention in the area of concentration of inhibitor considered

This behavior of inhibitors in aqueous solution is actually extrapolable to solutions, containing an oily phase, corresponding according to the invention

Claims (18)

1. Composition which may be used to impart temporary protection from corrosion to metal surfaces, comprising an oil-in-water emulsion, characterised in that the emulsion comprises in its aqueous phase at least one compound of general formula I

   

   wherein the groups R, R₁ and R₂ independently of one another denote a hydrogen atom, a C₁ to C₂₀ alkyl group, a C₁ to C₂₀ haloalkyl group where the halogen may be chlorine, bromine, iodine or fluorine, a C₃ to C₆ cycloalkyl group, a carboxyl function or a C₁ to C₆ carboxyalkyl group,

   n is an integer varying from 1 to 3 and

   X denotes a sulphur or oxygen atom,

   in the form of one of the water-soluble salts thereof.
2. Composition according to claim 1, characterised in that the compound of general formula I is preferably selected from among the water-soluble salts of benzothiazolylthiosuccinic acid, α-(benzothiazolylthio) stearic acid, α-(benzothiazolylthio)lauric acid, α-(benzothiazolylthio)caproic acid and α-(benzothiazolylthio)caprylic acid.
3. Composition according to one of the preceding claims, characterised in that the compound of general formula I is a water-soluble salt of benzothiazolylthiosuccinic acid.
4. Composition according to claim 3, characterised in that it is preferably the ethanolamine or ammonium salt thereof.
5. Composition according to one of the preceding claims, characterised in that its pH is between 8.2 and 9.5.
6. Composition according to one of the preceding claims, characterised in that the emulsion comprises, dispersed in water, 3 to 13% of an oily phase comprising 75 to 90% by volume of at least one oil, 5 to 10%; by volume of at least one surfactant and optionally 5 to 15% by volume of a corrosion inhibitor.
7. Composition according to one of the preceding claims, characterised in the emulsion comprises, dispersed in the aqueous phase, between about 3 and 8%, preferably about 6% by volume of an oil.
8. Composition according to claim 6 or 7, characterised in that it is a mineral oil and preferably an oil of the paraffinic or naphthenic type or a mixture thereof.
9. Composition according to one of claims 6 to 8, characterised in that the corrosion inhibitor of the oily phase is a carboxylic acid, a barium or sodium alkyl sulphonate or a salt of amine and fatty acid.
10. Composition according to one of the preceding claims, characterised in that the compound of general formula I is present in the composition in a concentration of between 1 and 10 g/l of emulsion.
11. Composition according to claim 10, characterised in that it contains from 1 to 3.5 g/l of compound of general formula I.
12. Composition according to one of the preceding claims, characterised in that it contains between 1 and 3.5 g/l of benzothiazolylthiosuccinic acid in the form of a water-soluble salt, in the aqueous phase of an emulsion containing 6% of soluble oil.
13. Composition according to claim 12, characterised in that it is ammonium benzothiazolylthiosuccinate, present in a concentration of the order of 2.5 g/l.
14. Process for preparing a composition according to one of claims 1 to 13, characterised in that the compound or compounds of general formula I is or are incorporated in the form of an aqueous solution in the aqueous phase of the emulsion prior to its emulsification with the oily phase.
15. Process for temporarily protecting a metal part from corrosion, characterised in that it comprises the steps consisting of:

    applying to at least part of said metal part a composition as defined in claims 1 to 13 or obtained according to claim 14 and

    drying said coated metal part until a dry film is obtained.
16. Process according to claim 15, characterised in that the composition is applied so as to saturate the adsorption sites on the surface of the metal part with a compound of general formula I and at the end of the heating of said composition to obtain a dry film, the compound of general formula I is not found to be present in the thickness of the film applied.
17. Metal part coated with a dry film for temporary protection from corrosion, obtained according to the process of claim 15 or 16, from a composition as defined in one of claims 1 to 13, or obtained according to claim 14.
18. Metal-part according to claim 17 with a surface density of dry film of between 0.3 and 2 g/m².

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