EP0010485B1 - Corrosion inhibitor composition, process for its preparation and its use in protecting metal surfaces - Google Patents

Description

The present invention relates, as a new industrial product, to a corrosion-inhibiting composition. It also relates to its preparation process and its application in the protection of metal surfaces, in particular with respect to corrosion in the presence of water in liquid or vapor form.

It is known that any metallic surface of current industrial use, and that any material composed of one or more metals, such as iron and its alloys, in particular galvanized steel, copper and its alloys, aluminum and its alloys , to name only the most used, are subjected, in contact with water, to troublesome transformations, generally called "corrosion phenomena".

We also know that the differences between the respective dissolution potentials of the various metals lead, on contact with water, to the formation of electrochemical couples, further aggravating the phenomena of preferential degradation of certain metals over others. These corrosion phenomena are all the more important and cumulative as the additions of new water are themselves frequent, or significant in quantities. It is more and more observable that by improving, from the point of view of output, industrial equipment becomes both more expensive and more sensitive to various corrosions.

Finally, it is known that, as a result of the increase in the need for water of various qualities, the latter see their characteristics vary quite strongly, in times sometimes very short, in particular with regard to their dissolved or combined gas contents. , in corrosive salts, or in precipitable salts in encrusting forms. Pre-physicochemical water treatment very rarely excludes the necessary use of a treatment or "conditioning" by means of corrosion inhibitors introduced into pretreated water and intended to provide artificial protection for most of the component metals the installations. Such protective packaging can be produced using numerous mineral substances, such as phosphates, polyphosphates, chromates, silicates, nitrites, sulfites, etc., or organic, such as thiols, thiazols, amines, tannins, etc., and chosen according to the characteristics of the water used and the installations themselves. However, most of these substances do not, when taken separately, have sufficiently broad inhibitory effects and must almost, in all cases, either be combined with one another or be dosed separately, which necessitates costly monitoring by a highly qualified staff. Everything that has just been mentioned contributes to making complicated and too often random the methods of protection of industrial or real estate installations of heating, air conditioning, cooling or energy production, using water as transfer fluid.

Among the organic or organo-mineral substances, the most used to date, and possessing corrosion-inhibiting properties, appear in particular phosphorus derivatives of amines, and the amines themselves. Among the phosphorus derivatives which have been proposed as corrosion inhibitors, mention may be made of aminophosphonic acids and their water-soluble salts described in French patents Nos. 1,430,798, 1,453,022, 1,461,087 and 1,474,068 and patent applications French published n ° 2 060 416, 2 144 900, 2 148 260, 2 174 091, 2 184 939, 2 184 940 and 2 259 105. Without explaining the protective action mechanism of these products, these documents set out the precise conditions in which these aminophosphonic acids must be neutralized stoichiometrically by mineral or organic bases, and associated with water-soluble salts of polyvalent metal cations, such as certain zinc and chromium salts, and with certain organic inhibitors containing sulfur. However, it should be noted that the aminophosphonic acids previously described are always presented and used in the form of water-soluble compounds to produce effects reducing the corrosion of metals at a loss of thickness always greater than or equal to 100 μ / year, at the dose of 5 ppm, in particular with respect to ferrous metals.

On its t ⁱ which was also proposed to use as corrosion inhibitors amines having a molecular weight less than 300 such as ammonia, hydrazine, alkylamines (especially C ₁ -C _4), morpholine, benzylamine, cyclohexylamine, alkanolamines (see in particular the published French patent application No. 2 310 420) and polyalkylene polyamines (see in particular the American patents No. 3 069 225 and 2 857 333 and Dutch No. 100 963 ), and their water-soluble salts obtained in particular by stoichiometric neutralization by means of aminophosphonic acids described in the abovementioned documents or of polyphosphonic acids. Said amines and their phosphonates lead to insufficient inhibition of the corrosion of metals, in particular by water, in the sense that the loss of thickness of the metallic surfaces which it was desired to protect is of the order of 80 to 150 plan in the best conditions of employment.

It is also known that it has been proposed to use fatty C ₁₂ -C ₂₂ alkylamines, in particular dehydroabietylamine, laurylamine and stearylamine, and their acid addition salts with HCl and CH ₃ COOH, as well as aliphatic polyamines with long chains called "fatty polyamines" (cf. French patent No. 1,435,023) such as stearylaminopropyleneamine. These fatty alkylamines and these fatty polyamines have the disadvantage of leading to insufficient inhibition of corrosion by water, since the loss of thickness of the metallic surfaces (in particular of Fe or Cu) is of the order of 80 to 100 µ / year under the best conditions of use.

In short, the inhibitors of the prior art and their salts best lead to a loss of thickness of the order of 80 to 150 plan.

The object of the present invention is to propose a new technical solution for solving the problem of inhibiting corrosion of metal surfaces, which is different from those of the prior art.

Another object of the invention is to propose a new inhibiting composition having an anti-corrosion power greater than that of the means which have been previously recommended. Indeed, in very many cases, rates of residual corrosion by water (loss of thickness from 80 to 150 u / year) are still considered too high with regard to the costs of repair and maintenance of the installations, also although with regard to production or operating stoppages, which these repairs or replacements very often cause. Thus compared to the solution of published French patent application no. 2 310 420 which consists in using a water-soluble corrosion inhibiting composition comprising (i) a mixture of alkanolamines and (ii) a phosphonic acid derivative (in particular l 1-hydroxy-ethylidene-1,1-diphosphonic acid or aminomethylenetriphosphonic acid), the technical solution according to the invention leads to better results: the rates of corrosion by city water, according to the invention, expressed in percentage compared to the witnesses are, for steel, lower than those of French application n ° 2 310 420, as this results from the comparison of tables II to IX below with tables II to IV of said application French above.

This is why, to overcome the drawbacks of the prior art, there is proposed, according to the invention, a new inhibitory composition which contains at least one polyamine and at least one derivative of alkylene phosphonic acid, and which makes it possible to achieve, for the metallic surfaces which it is desired to protect in particular with respect to water, losses of thickness less than or equal to 50 μ / year.

It has surprisingly been found that by mixing particular polyamines with derivatives of alkylenephosphonic acid (chosen from derivatives of aminoalkylenephosphonic acid and alkylene polyphosphonic acid), in non-stoichiometric ratios, an insoluble association is obtained in water but whose inhibitory properties, measured under identical conditions, are superior to those of water-soluble phosphonic acids used alone or in the form of salts with amines, and to those of polyamines alone or in their forms soluble in water water. It has been found, even more surprisingly, that the more insoluble in water the polyamine-alkylene phosphonic acid derivative combination, the better the inhibitory effect.

(où le group alkylène a une chaîne hydrocarbonée linéaire ou ramifiée, et les traits en pointillés représentent des liaisons avec d'autres groupes) comme indiqué dans le brevet français n° 1 430 798.By "aminoalkylenephosphonic acid derivative" is meant here the acids, salts and esters having in their molecule at least one fragment:

(where the alkylene group has a linear or branched hydrocarbon chain, and the dotted lines represent bonds with other groups) as indicated in French Patent No. 1,430,798.

By "derivative of alkylene polyphosphonic acid" is meant here a compound having at least two phosphonic functions and which is in particular chosen from the group consisting of. alkylene polyphosphonic acids, their esters and their mineral salts (such as in particular the metallic and NHQ salts), the alkylene chain comprising no amino group.

• a) au moins une polyamine ayant un poids moléculaire supérieur ou égal à 320 et répondant à la formule générale:
  
  dans laquelle R représente un radical hydrocarboné aliphatique saturé ou insaturé C₁₂-C₂₂; et n₁ représente un nombre entier compris entre 1 et 7 inclus, R et n₁ étant tels que le poids moléculaire de ladite polyamine soit supérieur ou égal à 320; et
• b) au moins un dérivé d'acide alkylènephosphonique tel que défini ci-dessus.

The corrosion-inhibiting composition according to the invention, which comprises at least one polyamine and at least one derivative of alkylene phosphonic acid, is characterized in that it comprises a water-insoluble association containing:

• a) at least one polyamine having a molecular weight greater than or equal to 320 and corresponding to the general formula:
  
  wherein R represents a saturated or unsaturated C ₁₂ -C ₂₂ aliphatic hydrocarbon radical; and n ₁ represents an integer between 1 and 7 inclusive, R and n ₁ being such that the molecular weight of said polyamine is greater than or equal to 320; and
• b) at least one derivative of alkylenephosphonic acid as defined above.

Among the polyamines of formula 1 which are suitable, mention may in particular be made of dodecyltri (aminopropylene) amine, dodecyltetra (aminopropylene) amine, hexadecyltri (aminopropylene) amine, hexadecenyltetra (aminopropylene) amine, octadecyl (aminopropylene) amine, octadecylpenta propylene) amine, octadecenyltetra (aminopropylene) amine, octadecyltri (aminopropylene) amine, octadecenylhexa (aminopropylene) amine and hexadecylhepta (aminopropylene) amine.

The amines of formula 1 can be used as they can be obtained commercially, alone or mixed together, in their pure or technical forms. It is also possible to use polyamines prepared from fatty acids of animal, vegetable or synthetic origin. Among the polyamines sold which are suitable, mention may in particular be made of the products known under the names brand DUOMEEN, DINORAM, TRINORAM, POLYRAM, LILAMIN and CEMULCAT which contain at least one polyamine I having a molecular weight greater than or equal to 320.

• - les acides de formule:
  
  dans laquelle Alk représente un groupe alkylène en C₁-C₈ à chaîne hydrocarbonée linéaire ou ramifiée;
• - les acides de formule:
  
  dans laquelle n₂ est un nombre entier compris entre 1 et 6 inclus;
• - l'acide di(hydroxyéthyl)aminométhylphosphonique de formuie:
  
• - les acides de formule:
  
  dans laquelle Z¹ est H ou un groupe alkyle en C₁-C₅; Z² est un groupe alkylène en C₂-C₅; Z³ est. un groupe alkylène en C₃-C₅; n₃ est un nombre entier compris entre 1 et 20 inclus et n₄ est un nombre entier compris entre 1 et 4.

Among the aminoalkylenephosphonic acid derivatives which are suitable according to the invention, mention may in particular be made of the following acids and their C ₁ -C ₄ alkyl esters (the acids being the preferred derivatives), namely:

• - the acids of formula:
  
  in which Alk represents a C ₁ -C ₈ alkylene group with a linear or branched hydrocarbon chain;
• - the acids of formula:
  
  in which n ₂ is an integer between 1 and 6 inclusive;
• - di (hydroxyethyl) aminomethylphosphonic acid of the form:
  
• - the acids of formula:
  
  wherein Z ¹ is H or a C ₁ -C ₅ alkyl group; Z ² is a C ₂ -C ₅ alkylene group; Z ³ is. a C ₃ -C ₅ alkylene group; n ₃ is an integer between 1 and 20 inclusive and n ₄ is an integer between 1 and 4.

Among the acids of formula II, non-limiting examples that may be mentioned include amino-tri (methylphosphonic), amino-tri (ethylphosphonic), amino-tri (propylphosphonic) and amino-tri (butylphosphonic), amino- tri [(α, α-dimethyl) methylphosphonic].

Among the acids of formula III, non-limiting examples that may be mentioned include ethylenediaminotetra (methylphosphinic), propylenediaminotetra (methylphosphonic) and hexamethylenediaminotetra (methylphosphonic) acids.

Among the acids of formula V, non-limiting examples that may be mentioned include diethoxypropylaminodi (methylphosphonic), undecaethoxypropylaminodi (ethylphosphonic) and pentapropoxypropylaminodi (methylphosphonic) acids.

dans laquelle:

• -A représente un groupe alkylène divalent comprenant une chaîne hydrocarbonée linéaire et saturée en C₁-C₁₀, chaque atome de carbone de ladite chaîne pouvant être, le cas échéant, substitué par au moins un groupe choisi parmi les groupes OH, alkyle en C₁-C₄ et phosphoniques
  
  et M₁, M₂, M₃, M₄, M₅ et M₆, identiques ou différents, représentent chacun H, un groupe alkyle en C₁-C₄, NH⁺ ₄ ou un cation métallique.

Among the alkylene polyphosphonic acid derivatives which are suitable, mention may in particular be made of the acids, esters and salts represented by the formula:

in which:

• -A represents a divalent alkylene group comprising a linear and saturated C ₁ -C ₁₀ hydrocarbon chain, each carbon atom in said chain possibly being substituted by at least one group chosen from OH, C alkyl groups ₁ -C ₄ and phosphonic
  
  and M ₁ , M ₂ , M ₃ , M ₄ , M ₅ and M ₆ , identical or different, each represent H, a C ₁ -C ₄ alkyl group, NH ⁺ ₄ or a metal cation.

où p est un nombre entire ayant une valeur comprise entre 0 et 8]. D'autres groupes A qui conviennent sont donnés ci-après.Among the groups A which are suitable, mention may in particular be made of the groups - (CH ₂ ) _m - [where m is an integer having a value between 1 and 10],

where p is an integer with a value between 0 and 8]. Other suitable groups A are given below.

Among the mineral salts included in the definition of formula VI, the preferred are the salts of NH ⁺ ₄ and of monovalent metals, such as the alkali metals Na and K.

• [A = CH₂], triméthylène-1,3-diphosphonique
• [A= (CH₂)₃], 1-hydroxyéthylidène-1,1-diphosphonique
• [A = >C(OH)CH₃], isopropylidène-diphosphonique
• [A = >C(CH₃)₂], 1-hydroxybutylidène-1,1-diphosphonique
• [A = >C(OH)CH₂CH₂CH₃], hexylidène-1,1-diphosphonique
• [A = >CH(CH₂)₄CH₃], 1-hydroxypropylidène-1,1-diphosphonique
• [A = >C(OH)CH₂CH₃], 1,4-dihydroxy-1,4-diméthyltétraméthylène-1,4-diphosphonique
  
• 1,2,3-tributyloctylidène-1,1-diphosphonique ou 1,2,3,4-tétrabutylbutylidène-1,1-diphosphonique
  
• 4-hydroxy-octylidène-1,1-diphosphonique ou 4-hydroxy-6-éthylhexylidène-1,1-diphosphonique
  
• 1,3-dihydroxy-2-éthylhexaméthylène-1,6-diphosphonique
  
• 1-éthyl-3-hydroxyhexaméthylène-1,1,6,6-tétraphosphonique
  
• 1,4-dihydroxytétraméthylène-1,4-triphosphonique
  
• 1,3-dihydroxyhexaméthylène-1,1,6,6-tétraphosphonique
  
• et hexaméthylène-1 ,6-diphosphonique [A=-(CH₂)₆-].

The most advantageous products of formula VI are alkylene polyphosphonic acids (M ₁ = M ₂ = M ₃ = M ₄ = M ₅ = M ₆ = H), in particular alkylene diphosphonic, alkylenetriphosphonic and alkylenetetraphosphonic acids. Among these, mention may in particular be made of methylene-1,1-diphosphonic acids

• [A = CH ₂ ], trimethylene-1,3-diphosphonic
• [A = (CH ₂ ) ₃ ], 1-hydroxyethylidene-1,1-diphosphonic
• [A => C (OH) CH ₃ ], isopropylidene-diphosphonic
• [A => C (CH ₃ ) ₂ ], 1-hydroxybutylidene-1,1-diphosphonic
• [A => C (OH) CH ₂ CH ₂ CH ₃ ], hexylidene-1,1-diphosphonic
• [A => CH (CH ₂ ) ₄ CH ₃ ], 1-hydroxypropylidene-1,1-diphosphonic
• [A => C (OH) CH ₂ CH ₃ ], 1,4-dihydroxy-1,4-dimethyltetramethylene-1,4-diphosphonic
  
• 1,2,3-tributyloctylidene-1,1-diphosphonic or 1,2,3,4-tetrabutylbutylidene-1,1-diphosphonic
  
• 4-hydroxy-octylidene-1,1-diphosphonic or 4-hydroxy-6-ethylhexylidene-1,1-diphosphonic
  
• 1,3-dihydroxy-2-ethylhexamethylene-1,6-diphosphonic
  
• 1-ethyl-3-hydroxyhexamethylene-1,1,6,6-tetraphosphonic
  
• 1,4-dihydroxytetramethylene-1,4-triphosphonic
  
• 1,3-dihydroxyhexamethylene-1,1,6,6-tetraphosphonic
  
• and hexamethylene-1, 6-diphosphonic [A = - (CH ₂ ) ₆ -].

The alkylene phosphonic acids corresponding to formulas II to VI above can be chemically pure products, or technical products normally manufactured by industry and sold in liquid, pasty or pulverulent form, or alternatively in the form of aqueous solutions at all concentrations, without the choice of one of these forms of presentation being able to constitute any limitation to the present invention. However, in general, for commercial reasons and for convenience, alkylenephosphonic acids placed on the market in the form of aqueous solutions will be preferred.

Advantageously, the composition according to the invention will contain (a) 5 to parts by weight of polyamine I and (b) 20 to 95 parts by weight of the alkylenephosphonic acid derivative and, preferably, (a) 15 to 70 parts by weight of polyamine I and (b) 30 to 85 parts by weight of alkylene phosphonic acid derivative of formulas II to VI.

The process for preparing the corrosion-inhibiting composition is carried out according to a method known per se which consists in mixing one or more polyamines with one or more derivatives of alkylene phosphonic acid. According to the best mode that is recommended, use is made of a process which is characterized in that the selected polyamine or polyamines are brought to the liquid state, by sufficient heating, which are gradually introduced, with moderate stirring. , or bright, as the case may be, 'in an aqueous solution of the alkylenephosphonic acid (s) chosen and previously heated to a temperature lower than that of the polyamine.

Depending on the nature of the means a and b which are used, the mixture which is obtained may be in the form of a gel, or a paste, or a wax.

In practice, the polyamine (s) will be melted at a temperature between approximately 30 and approximately 85 ° C. and poured into the alkylene phosphonic acid (s) brought to a temperature between approximately 15 and approximately 60 ° C.

It is easily understood that, when the metal surfaces to be protected are at low temperatures, more precisely at temperatures below 60 ° C., such as the metal surfaces of air humidifiers, condensers, chilled water networks, it will be preferable to choose those, among the alkylenephosphonic acids corresponding to the general formulas (II) to (VI) above, and those, among the aliphatic polyamines corresponding to the general formula (I) above, which give, as a mixture, compositions having softening points as low as possible. Similarly, mixtures with higher softening points will be preferred as corrosion inhibitors with respect to metal surfaces subjected to high temperatures, such as for example those constituting the tubes of steam boilers, or superheaters, or else those constituting the cooling circuits of the ovens of the metallurgical and steel industries.

For practical reasons and, in particular, the fact that most alkylene phosphonic acids are only commercially available in the form of more or less concentrated aqueous solutions, it is not economically advisable to remove the water. of the composition according to the invention, since it is specifically intended in particular to be redispersed in water for its use as a corrosion inhibitor. In addition, this water not reacting with any of the constituents of the composition according to the invention, and obviously not intervening in its corrosion-inhibiting properties, only serves as a medium for dispersing said composition according to the commercial aspect. that we want to give it. Also, the very variable amounts of water that said composition may contain cannot constitute any limitation to the present invention.

The pasty or gelled compositions produced according to the invention can be introduced using a piston positive displacement pump, as is commercially available, either as is in water in industrial or real estate circuits. to be protected, either still previously emulsified, or dispersed in a larger amount of water using one or more surface-active substances of commerce and known to those skilled in the art as capable of dispersing polyamines oily. The quantities of substances with surface-active properties used for this purpose depend on the commercial aspect which it is desired to give to such dispersions and should not constitute any limitation to the present invention.

In addition to the preferred application according to the invention described above, there is another anti-corrosion application according to which the metal parts that are to be protected are treated in particular by immersion by means of an inhibiting composition according to the invention, this inhibitory composition possibly being, if necessary, in the form of an aqueous bath.

By way of indication, the substances with surface-active properties which are the most recommended are those included among the nonionic and / or cationic surfactants preferably. Examples of non-ionic substances that may be mentioned are ethoxylated or propoxylated fatty acids and alcohols, ethoxylated fatty monoamines, fatty acid or alcohol esters, aliphatic amine oxides, sorbitol esters. , etc., and among the so-called cationic substances, amine salts, quaternary ammonium salts, condensation products of ethylene or propylene oxide on fatty polyamines.

Stable dispersions in water can be obtained in particular with known industrial products chosen from those which have brand names: NORAMOX, ETHOMEEN, DINORAMOX, ETHODUOMEEN, ETHOQUAD, ARQUAD, NORAMIUM, NOXAMINE, ADOGEN, ELFAPUR, AROMOX etc.

Other advantages and characteristics of the invention will be better understood on reading which will follow from examples of preparation which are in no way limitative but given by way of illustration.

Example 1

500 g of an aqueous solution at 40% by weight of aminotri acid (methylenephosphonic acid) therefore containing 200 g of acid, are placed in a glass container, or in any other material which is not liable to be damaged by acids. anhydrous aminotri (methylenephosphonic), corresponding to the general formula (II) above, at a homogeneous temperature of approximately 30 ° C. 500 g of oleylaminopropyleneamine, of industrial technical quality, corresponding to the general formula (Î) above, and previously liquefied, and maintained during the introduction, are gradually added into the warm acid solution, with moderate mechanical stirring. the temperature of about 45 ° C.

We then quickly obtain a thick paste, amber yellow in color.

The pasty composition thus obtained, which has a solubility of less than 1% by weight in distilled water, constitutes an excellent corrosion inhibitor according to the invention, as will be seen below.

Example 2

• C₁₈H₃₇⁅NH-(CH₂)₃⁆₃NH₂

préalablement chauffée, et maintenue à la température de 50°C. Lorsque le mélange est refroidi à la température ambiante, voisine de 20°C, on obtient un gel blanc crème, qui s'avère, à l'examen, une émulsion très fine d'une phase normalement insoluble dans l'eau. Une étude plus approfondie de la phase organique dispersée montre que sa solubilité dans l'eau est inférieure à 1 % en poids. Cette phase dispersée constitue en excellent inhibiteur de corrosion selon l'invention, ainsi que le démontrent les résultats donnés plus loin.According to the same operating process as in Example 1 above, 800 g of an aqueous solution at 30% by weight of pentapropoxypropylaminodi (methylenephosphonic) acid, that is to say containing 240 g, are heated to 40 ° C. of this aminophosphonic acid corresponding to the general formula (V) above which is maintained under moderate mechanical stirring. Then poured slowly into the acid solution, 243 g of stearyltri (aminopropylene) -amine of formula:

• C ₁₈ H ₃₇ ⁅NH- (CH ₂ ) ₃ ⁆ ₃ NH ₂

previously heated, and kept at the temperature of 50 ° C. When the mixture is cooled to ambient temperature, close to 20 ° C., a creamy white gel is obtained, which turns out, on examination, a very fine emulsion of a phase normally insoluble in water. A closer study of the dispersed organic phase shows that its solubility in water is less than 1% by weight. This dispersed phase constitutes an excellent corrosion inhibitor according to the invention, as demonstrated by the results given below.

Example 3

In a glass or stainless steel beaker of 1 liter capacity, 600 g of a 50% by weight solution of hexamethylenediaminotetra (methylenephosphonic acid) corresponding to the general formula are introduced at room temperature of 20 ° C. 111) above, and a stainless steel agitator is introduced capable of rapidly swirling the acid solution. 300 g of octadecenyltetra (aminopropylene) amine, corresponding to the general formula (I) above, which is gradually added to the solution, are brought to liquefaction, by slow heating to approximately 35 ° C. acid maintained with vigorous stirring. When all the polyamine has been introduced, the stirring speed is gradually reduced. The paste obtained after returning to room temperature appears, upon further study, as a reverse dispersion of water in an amber yellow organic phase, which turns out to have only a tiny solubility in water. This composition constitutes an excellent corrosion inhibitor, as the experiments set out below demonstrate.

Example 4

500 g of a 60% by weight aqueous solution of hexylidene-1,1-diphosphonic acid, thus containing 300 g, are placed in a glass container, or in any other material which is not liable to be damaged by acids. g of hexylidene-1,1-diphosphonic acid corresponding to formula VI above, to a uniform temperature of around 35 ° C. 250 g of oleyltri (aminopropylene) amine, of industrial quality, corresponding to general formula 1 above, and previously liquefied at a temperature of about 40 ° C., are gradually poured into the acid solution, with vigorous stirring.

One then quickly obtains a homogeneous gel, dark yellow in color, having a very low solubility in water constituting (despite this low solubility) an excellent corrosion inhibitor of the steel, copper and aluminum in the presence of water.

Example 5

400 g of a 62% by weight aqueous solution of 1-hydroxyethylidene-1,1-diphosphonic acid corresponding to general formula VI below are introduced into a glass or stainless steel container. above and which is subjected to slight agitation. Then introduced very gradually, in small quantities at a time, 200 g of octadecenyltetra (aminopropylene) amine, previously liquefied at a temperature of about 55 ° C. The dispersion obtained appears as a gelled milky emulsion, which turns out to be very sparingly soluble in water, and nevertheless has remarkable properties inhibiting the corrosion of metals in the presence of water, as demonstrated below.

Example 6

Under the same conditions as those of Example 5 above, 700 g of crystallized 1-hydroxyethylidene-1,1-diphosphonic acid are dissolved in 500 ml of water, brought to the temperature of approximately 50 ° C. trade, in order to obtain a solution of this acid at 58.33% by weight. When all the acid is well dissolved, 600 g of commercial oleylaminopropyleneamine, previously liquefied in a homogeneous manner at a temperature of approximately 30 ° C., are then introduced under vigorous stirring, and the stirring is continued until obtaining a homogeneous paste which no longer exhibits separation of the aqueous phase after the mixture has cooled to room temperature. When said paste, brown to dark yellow in color (depending on the industrial origins of the polyamine used) is then immersed in water, it practically does not dissolve therein; however, it has excellent inhibitory properties against metal corrosion.

In order to demonstrate the remarkable corrosion-inhibiting powers of the compositions according to the invention, corrosion tests were carried out in the presence and in the absence of said compositions. To do this, we built a unique experimental circuit, capable of reproducing, as faithfully as possible, the conditions existing in industrial circuits, either heating or cooling.

The circuit, mainly made of glass, with a total capacity of 19.6 I, surmounted by an expansion tank open to the air, also made of glass, of 5 I capacity, is fitted with a stopcock adjustable drain, usable either discontinuously for heating tests or continuously for cooling tests. The circulation flow of 1.6 m ³ / h is ensured by a centrifugal pump (in particular a centrifugal pump as manufactured by HALBERG GmbH of Ludwigshafen, RFA) and controlled using a rotameter. The straight sections of the circuit are made of industrial glass tubes, their diameter is 40 mm and their total length is 3 m. The water circulation speed there is about 1.5 m per second. Electric heating cords wound on the straight sections maintain the temperature that may be desired by means of a regulating device. In addition, in order to reproduce the influence of the various metals entering an industrial circuit, two series of brass and copper tubes, each 15 cm long, as well as three constantly open brass valves, were placed on the circuit. .

• - des éprouvettes de différents métaux pour les mesures de pertes en poids et pour examens visuels;
• - und sonde double, reliée à un analyseur électronique type CORRATER (commercialisé par la Sté MAGNA INSTRUMENTS ROHRBACK Corp. de Santa Fe Springs, Californie) muni d'un enregistreur, pour les mesures potentio-statiques de vitesse de corrosion, et d'un convertisseur permettant de mesurer alternativement la corrosion dite "généralisée" et celle dite "par piqûre" ("pitting"). Les électrodes spécifiques de l'analyseur potentio-statique CORRATER ont les références 60814-8001 pour les mesures sur l'acier, 60814-8061 pour les mesures sur le cuivre, et 60814-8080 pour les mesures sur l'aluminium.

The circuit also includes the means of monitoring the effectiveness of the inhibitors:

• - test pieces of different metals for weight loss measurements and for visual examinations;
• - a double probe, connected to an electronic analyzer type CORRATER (marketed by MAGNA INSTRUMENTS ROHRBACK Corp. of Santa Fe Springs, California) equipped with a recorder, for potentio-static measurements of corrosion speed, and a converter making it possible to measure alternately so-called "generalized" corrosion and so-called "pitting" corrosion. The specific electrodes of the CORRATER potentio-static analyzer have the references 60814-8001 for measurements on steel, 60814-8061 for measurements on copper, and 60814-8080 for measurements on aluminum.

The test pieces for weight loss measurements are of hollow cylindrical shape, 50 mm in length, 21.3 to 22 mm in outside diameter, and 14.8 to 17 mm in inside diameter, and develop an external surface of 33 , 45 to 34.55 cm ² , in contact with the aggressive medium, for an average weight of 72.5 g for steel test pieces, 69.0 g for copper test pieces and 21.2 g for test pieces in aluminium.

Before the tests, the metal test pieces are polished using a soft commercial abrasive, washed with demineralized water, dried with acetone and weighed very exactly to ± 1 _X 10- ⁴ g. They are then mounted in series, three by three, each of different metal, separated and held together by an appropriate Teflon fixing system, then introduced horizontally into a straight glass section of the circuit. At the end of the tests, they are removed from the circuit, brushed using a soft brush to remove corrosion products, washed with demineralized water, dried with acetone and weighed very exactly to ± 1 x 10 ^-4 g.

• -des analyses hebdomadaires de l'eau du circuit;
• - un dosage quotidien de la teneur de l'eau en inhibiteur;
• -des mesures de perte de poids des éprouvettes métalliques;
• -des mesures potentiostatiques des vitesses de corrosion sur les électrodes de l'appareil CORRATER;
• - un examen visuel des éléments métalliques du circuit lui-même.

The controls of the inhibitory properties of the compositions tested consisted of:

• - weekly analyzes of the water in the circuit;
• - a daily dosage of the water content in inhibitor;
• - weight loss measurements of metal test pieces;
• - potentiostatic measurements of the corrosion rates on the electrodes of the CORRATER device;
• - a visual examination of the metallic elements of the circuit itself.

The tests were carried out with two varieties of water, namely raw water (raw water AI for the inhibiting compositions of examples 1-3, and raw water A2 for the inhibiting compositions of examples 4-6) and softened water ( softened water B1 for the inhibitor compositions of Examples 1-3, and softened water B2 for the inhibitor compositions of Examples 4-6, the softened water B1 and respectively B2 being obtained from raw water A1 and respectively A2 by passage over exchange resin ionic, cationic type in sodium cycle).

The characteristics of waters A1 and B1, on the one hand, and waters A2 and B2, on the other hand, are given in table 1 below.

Raw water A1 and A2 (drinking water distributed by the city of Paris) was used as such for corrosion tests of the "cooling" type, and softened water B1 and B2 was used for corrosion tests of the "heater".

Due to the permanent presence of dissolved oxygen, such softened waters are deemed to be very aggressive as evidenced by the losses in thickness of the test specimens for blank tests appearing in Tables II to V below.

dans laquelle:

• P = perte de poids exprimée en milligrammes;
• J = nombre de jours d'exposition au milieu agressif;
• S = surface externe de l'éprouvette exprimée en cm2;
• d = masse spécifique du métal de l'éprouvette en g/cm³.

To simplify the reading of Tables II to IX which follow, the results are directly translated into thickness losses, expressed in microns per year, and deducted from the weight losses measured using the formula below:

in which:

• P = weight loss expressed in milligrams;
• D = number of days of exposure to the aggressive medium;
• S = external surface of the test piece expressed in cm2;
• d = specific mass of the metal of the test piece in g / cm ³ .

In addition, the corrosion percentages calculated from said thickness losses were given, the blank control having a corrosion percentage of 100%.

"Heating" type corrosion tests.

The results of the corrosion tests of the "heating" type have been given in Tables II to V below. Tables II and III relate to the weight loss measurements, and Tables IV and V to the potentiostatic measurements to assess the corrosion rates (expressed in µ-years).

In order not to immobilize the circuit for too long, the blank measurements, that is to say in the absence of inhibitor, were carried out for only 15 days, while the tests in the presence of inhibitor were continued for two months, for each composition tested and at two different dosages, in an approximate ratio of 10 to 1, depending on the mechanical possibilities of dispersion in water of the compositions of Examples 1 to 6 above, without the use of an agent surfactant.

Long-term tests, ie 60 days, which are preferable in the presence of the non-stoichiometric inhibitor compositions according to the present invention, do not allow intermediate measurements of weight loss, which would require frequent handling, sources of inaccuracies. This is why the potentiostatic corrosion rate measurements were carried out jointly and their recording gave completely comparable results, which are shown in Tables IV and V below.

At the end of the tests, examination under the microscope shows that all the test pieces are free from "pitting", which seems normal since the CORRATER readings in switching "pitting + corrosion" were identical to ± 5 microns per year. The steel specimens remained very smooth, but not shiny, of slightly brown color. The copper and aluminum test pieces retained, in all cases, their shiny surfaces without any change perceptible under the microscope. The other metallic elements of the circuit appear intact and without deposit or corrosion.

"Cooling" type corrosion tests.

For the "Cooling" type tests, the circuit was modified by the introduction into its straight section of a hollow steel probe, 240 mm in length and 28 mm in outside diameter, provided with an electric heating resistor adjustable to the using a rheostat.

The metal test pieces intended for weight loss measurements and the "CORRATER" probe are kept as for the "Heating" type tests. The circuit is filled, then continuously supplied, with raw water from the city of Paris, having the characteristics indicated in Table I, and at a rate of approximately 20 I per hour leading to a renewal of the water in the circuit every hour on average. The purge is adjusted continuously so as to keep the water level in the expansion tank constant. The pasty inhibitor, according to the compositions of the invention, is simply immersed in the expansion vessel using a cotton cloth sachet. The temperature of the water, kept in forced circulation by the centrifugal pump, and measured using a thermometer placed downstream of the heated probe, stabilizes at 50 ° C ± 5 ° C.

The duration of each test is 15 days without and with the inhibitors of Examples 1 to 6 above. The same measurements as for the "Heating" type tests are carried out, with the difference, however, that at the end of the tests the cylindrical samples in steel, copper and aluminum, as well as the heated steel probe, are washed , before brushing, using a dilute solution of passivated sulfamic acid, in order to eliminate any deposits of mineral salts which may come from the hardness of the raw water than the phosphonic acids, present in possibly insufficient quantities in the compositions according to the invention would not have prevented.

The results are shown in Tables VI to IX below. Tables VI and VII relate to weight loss measurements and Tables VIII and IX to potentiostatic measurements to assess the corrosion rates.

The potentiostatic measurements carried out simultaneously using the "CORRATER" electronic analyzer give values quite comparable to those resulting from the weight loss measurements, as shown in Tables VIII and IX below.

At the end of the tests, most of the test tubes as well as the heated probe, appear covered with a very fine white powder which is easily removed with a soft brush, even on the heated probe. Washing with dilute sulfamic acid is however carried out as a precaution.

Examination under the microscope shows that all test tubes and the heated steel probe are perfectly free from pitting. The steel samples are smooth, slightly brown in color, more pronounced on the heated probe. The copper and aluminum specimens are slightly less shiny than in the "Heating" type tests. The other metallic elements of the circuit appear after disassembly, brushing and rinsing with sulfamic acid perfectly free of corrosion deposits and without any visible attack.

All the results in Tables II to IX demonstrate the remarkable inhibitory properties of the compositions according to the invention, since no corrosion could be equal to or greater than 50 μ / year for the steel, to 7 μ / year for the copper and planar for aluminum, for the compositions of the examples 4 to 6. The results of compositions 1 to 3 are better in the sense that no corrosion could be equal to or greater than 40 µ / year for steel, 7 µ / year for copper and 2 µ / year for aluminum. Examples 1 to 6 and Tables II to IX also demonstrate that the significant variations in nature and in respective proportions of the constituents of the compositions according to the invention have no significant influence on the inhibitory properties of said compositions. It is also remarkable that the compositions according to the invention do not require an adjustment of the pH of the corrosive medium or the addition of specific inhibitors with respect to copper in particular. It is finally remarkable that at doses of the order of 5 parts per million, the compositions according to the invention manifesting a corrosion inhibiting power very much greater than the inhibiting powers of each of their constituents taken separately, at doses substantially more high.

Claims (14)

1. An anti-corrosion composition comprising at least one polyamine and at least one alkylenephosphonic acid derivative, characterized in that it comprises a water-insoluble association containing

a) at least one polyamine with a molecular weight higher than or equal to 320 and answering to the general formula

wherein R is a saturated or unsaturated aliphatic C₁₂-C₂₂- hydrocarbon radical; and n₁ is an integer varying between 1 and 7 inclusive, R and n₁ being such that the molecular weight of the said polyamine is greater than or equal to 320; and

b) at least one alkylenephosphonic acid derivative selected from the group constituted by the aminoalkylene-phosphonic acid derivatives and the alkylene polyphosphonic acid derivatives.

2. A composition according to claim 1, characterized in that the aminoalkylenephosphonic acid derivative is selected from the group consisting of:

(i) the acids of the formula

wherein Alk is a C₁-C₆ alkylene group, having a straight or branched hydrocarbon chain, and

(ii) their C₁--C₄-alkyl esters.

3. A composition according to claim 1, characterized in that the aminoalkylenephosphonic acid derivative is selected from the group consisting of:

(i) the acids of the formula

wherein n₂ is an integer varying between 1 and 6 inclusive; and

(ii) their C₁-C₄-alkyl esters.

4. A composition according to claim 1, characterized in that the aminoalkylenephosphonic acid derivative is selected from the group consisting of:

(i) di(hydroxyethyl)aminomethylphosphonic acid of the formula

and

(ii) its C₁-C₄-alkyl esters.

5. A composition according to claim 1, characterized in that the aminoalkylenephosphonic acid derivative is selected from the group consisting of:

(i) acids of the formula

wherein Z¹ is H or a C₁-C₅-alkyl group; Z² is a C₂-C₅-alkylene group; Z³ is a C₃-C₅-alkylene group; n₃ is an integer varying between 1 and 20 inclusive, and n₄ is an integer varying between 1 and 4; and

(ii) their C₁-C₄-alkyl esters.

6. An anti-corrosion composition according to claim 1, characterized in that the alkylenephosphonic acid derivative is a compound selected from the group consisting of from alkylenepolyphosphonic acids comprising at least two P0₃H₂ functions, their esters and salts.

7. An anti-corrosion composition according to claim 1, characterized in that the alkylenepolyphosphonic acid derivative answers to the general formula

wherein A is a bivalent alkylene group comprising a straight and saturated C₁-C₁₀-hydrocarbon chain, each carbon atom of which chain can be, if necessary, substituted by at least a group selected from OH, C₁-C₄-alkyl and phosphonic groups of the formula

and M,, M₂, M₃, M₄, M_s and M_e which can be identical or different, are each H, a C₁-C₄-alkyl group, NHQ or a metal cation, such as Na⁺ and K⁺.

8. An anti-corrosion composition according to claim 7, characterized in that the alkylenepolyphosphonic acid derivative is an acid of the formula VI wherein M₁=M₂=M₃=M₄=M₅=M₆-H.

9. An anti-corrosion composition according to claim 1, characterized in that it comprises:

a) 5 to 80 parts by weight of polyamine I, and

b) 20 to 95 parts by weight of alkylenephosphonic acid derivative.

10. An anti-corrosion composition according to claim 1, characterized in that it comprises:

a) 15 to 70 parts by weight of polyamine I, and

b) 30 to 85 parts by weight of alkylenephosphonic acid derivative.

11. A composition according to any one of claims 1, 9 and 10, characterized in that it is the form of a suspension or dispersion in water and, if necessary, comprises a surface-active agent.

12. A process for the preparation of an anti-corrosion composition, characterized in that it consists in introducing the polyamine I in an aqueous solution of an alkylenephosphonic acid derivative such as defined hereinabove, the temperature of the said derivative in aqueous solution being less than that of the polyamine I.

13. A method of treating water in order to prevent corrosion of a metallic surface by means of a composition according to any one of claims 1 to 11, said method being characterized in that said metallic surface is treated with an aqueous suspension or dispersion comprising an anti-corrosion composition as claimed in any one of claims 1 to 11 and optionally a surface-active agent.

14. A method according to claim 13 in order to prevent corrosion of metallic surface in contact with water, characterized in that the aqueous suspension or dispersion, comprising an anti-corrosion composition as claimed in any one of claims 1 to 11, and optionally a surface-active agent, is introduced into the water circuits.