EP0025624A1 - Process for inhibiting the corrosion of a metallic installation upon contact with an acidic bath - Google Patents

Process for inhibiting the corrosion of a metallic installation upon contact with an acidic bath Download PDF

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Publication number
EP0025624A1
EP0025624A1 EP80200835A EP80200835A EP0025624A1 EP 0025624 A1 EP0025624 A1 EP 0025624A1 EP 80200835 A EP80200835 A EP 80200835A EP 80200835 A EP80200835 A EP 80200835A EP 0025624 A1 EP0025624 A1 EP 0025624A1
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Prior art keywords
bath
installation
process according
ferric ions
cyanide complex
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EP80200835A
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German (de)
French (fr)
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EP0025624B1 (en
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Daniel Tytgat
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Solvay SA
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Solvay SA
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
    • C23F11/00—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent
    • C23F11/04—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in markedly acid liquids
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
    • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
    • C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
    • C23G1/04—Cleaning or pickling metallic material with solutions or molten salts with acid solutions using inhibitors

Definitions

  • the present invention relates to a method for inhibiting corrosion of metallic installations in contact with an acid bath. It relates more particularly to a process for inhibiting corrosion, in contact with aqueous baths containing a mineral acid, of installations made up of metals less noble than hydrogen in these baths.
  • the acid baths used in these pickling and descaling processes must generally contain a corrosion inhibitor whose role is to avoid deterioration of the installation without harming the pickling or descaling action of the bath.
  • Corrosion inhibitors added to acid baths also have the function of preventing corrosion of installations used for their handling, in particular storage tanks, manifolds and their accessories such as valves, valves and pumps.
  • alkylpyridinium chloride As a corrosion inhibitor, it has been observed, in practice, that despite the presence of alkylpyridinium chloride in the acid baths, these nevertheless cause, in some cases, corrosion, sometimes rapid, of the installation.
  • a known method for overcoming this drawback consists in adding stannous chloride to the bath, in addition to the alkylpyridinium chloride.
  • etching paste made up of a mixture of phosphoric acid, potassium ferrocyanide, urea, phosphate. zinc, sawdust, molasses and decylpyridinium chloride (Chemical Abstracts, 1976, vol.85, no. 97486d).
  • the invention aims to remedy the aforementioned drawbacks of known methods, by providing a method for preventing corrosion of metallic installations in contact with acid baths containing alkylpyridinium chloride, which is both inexpensive and harmless for the environment. .
  • the invention therefore relates to a method for inhibiting corrosion in contact with an aqueous bath containing a mineral acid and alkylpyridinium chloride, from a metal installation less noble than hydrogen in said bath or an alloy containing such a metal; according to the invention, a soluble cyanide complex is added to the bath, capable of forming an insoluble compound by reaction with ferric ions of the bath, the cyanide complex being added to the bath in an amount adjusted between that necessary to maintain in the bath, at contact with the installation, a concentration of ferric ions equal to 30 mg / kg and that strictly necessary to obtain a zero concentration of ferric ions.
  • the expression “metal less noble than hydrogen in the bath” is intended to denote any metal whose equilibrium potential in the acidic aqueous bath considered is less than the equilibrium potential of hydrogen in the same bath and under the same conditions of use. In other words, these are metals which, in the event of corrosion in contact with the bath, generate hydrogen evolution (Atlas of electrochemical equilibria - M. Pourbaix - Gauthier - Villars & Cie, Editeurs - 1963 - p.75 and 76). Chromium, iron, cobalt, nickel and zinc are examples of metals which fall within the scope of the invention.
  • alloy of such a metal is intended to denote all the alloys of which at least one of the constituent elements is a metal less noble than hydrogen, as defined above. It therefore designates both alloys less noble than hydrogen (for example ordinary steel and cast iron) and alloys more noble than hydrogen (for example cupronickels which are nickel and copper alloys containing from 70 to 85% copper).
  • the choice of mineral acid for the bath is not critical and essentially depends on the nature of the treatment.
  • the mineral acid is advantageously hydrochloric acid
  • the bath consisting for example of an aqueous solution containing 0.01 to 3 moles of hydrochloric acid per liter.
  • Normal hydrochloric acid solution is suitable particularly suitable as a bath for the treatment of iron or iron alloy installations.
  • alkylpyridinium chloride The function of alkylpyridinium chloride is to prevent corrosion of the installation by acid. It is preferably chosen from those derived from alkanes having from 10 to 18 carbon atoms. Cetyl-, myristyl- and laurylpyridium chloride have been found to be particularly advantageous.
  • the content of alkylpyridinium chloride in the bath depends on various factors, in particular the choice of acid, the concentration, of the bath in this acid, the temperature of the bath, the nature of the material of the installation, the duration of treatment of the installa- ation with the bath and the choice of alkylpyridinium chloride. It can be determined in each particular case by routine laboratory work.
  • the bath is a normal solution of hydrochloric acid
  • good results are generally obtained by fixing the content of aikylpyridinium chloride in the bath between 0.5 and 5000 mg / kg, preferably between 2 and 500 mg / kg.
  • the preferred baths for the treatment of mild steel or cast iron installations are normal hydrochloric acid solutions containing approximately 75 to 200 mg of laurylpyridinium chloride per kg of solution.
  • a soluble cyanide complex is added to the bath, capable of reacting with ferric ions of the bath to form an insoluble compound.
  • ferric ions in the bath can come from various sources. They can in particular come from the installation itself, when the latter is made of iron or an iron alloy, either because they result from corrosion of the installation, or because they are located in an inlay dissolved in the bath in the case of a descaling treatment. These ions can also result from local corrosion of an iron-based element, external to the installation proper and with which the bath is brought into temporary contact.
  • Cyanide complexes constitute a class of very stable chemical complexes, well known in the art (Encyclopedia of Chemical Technology - Kirk & Othmer - The Interscience Encyclopedia, Inc. - 19 - Vol. 4, p. 677 to 680). They consist of complex anions containing at least one central metallic atom linked by coordination to cyanide groups.
  • the cyanide complex must be chosen from those which are soluble in acidic aqueous baths and which, by reaction with ferric ions, form insoluble cyanide compounds.
  • ferricyanide and ferrocyanide complexes are examples of cyanide complexes which are very suitable in the context of the invention.
  • tetravalent cyanide complexes and more particularly ferrocyanide.
  • the cyanide complex can be introduced into the bath in the form of a water-soluble compound.
  • Water-soluble compounds which have been found to be particularly advantageous are hexacyanoferric acid and ferrocyanides of calcium, ammonium, sodium and potassium, potassium ferrocyanide being preferred.
  • the addition of soluble cyanide complex should be limited to the maximum of the quantity strictly necessary to achieve a zero concentration of ferric ions in the bath, in the immediate vicinity of the installation.
  • the quantity of this soluble cyanide complex added to the bath must moreover be sufficient to maintain the residual content of ferric ions in the bath in the vicinity of the installation, at all times below a critical value from which their influence on corrosion of the installation becomes unacceptable.
  • the fixing of the above critical value of the residual content of ferric ions in the uain in the vicinity of the installation will depend on a large number of parameters, such as the nature of the material of the installation, the nature and concentration of the mineral acid in the bath, the temperature of the bath, the duration of the treatment.
  • the addition of the soluble cyanide complex should be adjusted so that the residual content of ferric ions in the bath in contact with the installation does not exceed 30 mg / kg.
  • Values which are very suitable for the quantity of cyanide complex added to the bath are those which lead to obtaining a residual content of ferric ions in the bath in contact with the installation, of between 20 and 0.5 mg / kg , preferably between 5 and 1 mg / kg.
  • Any suitable technique can be used to control the amount of cyanide complex added to the bath.
  • the quantity of soluble cyanide complex added to the bath is adjusted by measuring the potential of the material of the installation in the bath.
  • the magnitude of the potential of the material of the installation in the bath is a measure of its ferric ion content.
  • the method used to measure the potential of the installation material in the bath is not critical.
  • an electrochemical measuring cell comprising a reference electrode (for example a hydrogen electrode or a calomel electrode) and a working electrode executed in the same material as the installation and immersed in the bath in the immediate vicinity of the installation.
  • the working electrode can be a metal bar, for example, a cylindrical bar.
  • an area of the installation which is in contact with the bath for example the wall of a tank, a pipe, the shutter valve of a valve or the impeller or volute of a pump.
  • the method according to the invention finds an interesting application for the descaling of evaporators made of nickel or of nickel alloy used to crystallize sodium chloride from caustic brines produced by electrolysis of a sodium chloride brine in a cell. permeable diaphragm electrolysis.
  • Another interesting application of the process according to the invention lies in the descaling of the refrigeration zone of the columns used for the crystallization of sodium bicarbonate in the process for the manufacture of soda with ammonia (Manufacture of soda -Te-Pang Hou - Hafner Publishing Co - 1969).
  • the method according to the invention can also be applied to the handling of mineral acids in aqueous solution, in metal pipes or tanks.
  • the material of the installation is an alloy comprising both a metal less noble than hydrogen, as defined above, and a metal more noble than hydrogen
  • Potassium iodide is a preferred substance for inhibiting corrosion of such metals.
  • cupronickels which are nickel and copper alloys generally containing from 70 to 85% of copper and from 15 to 30% of nickel (Treaty of Structural Metallurgy - A. De Sy and J. Vidts - Dunod - 1962 - p.184).
  • an electrochemical measuring cell comprising a working electrode, executed in the material studied and immersed in a normal aqueous solution of hydrochloric acid, containing, per kg, 100 mg of the product known under the name "Dehyquart C "(Henkel Int. GmbH) which consists mainly of laurylpyridinium chloride.
  • the working electrode consisted of a cylindrical bar whose surface in contact with the bath had an area equal to 10 cm 2 .
  • the test was carried out with an ordinary steel working electrode.
  • the second phase of the test was immediately started, during which five consecutive additions of potassium ferrocyanide trihydrate were made to the solution of the measuring cell.
  • the consecutive additions of potassium ferrocyanide were adjusted so that its residual content of ferric ions was successively reduced to 300, 100, 30, 10 and 0 mg / kg.
  • the results of this second phase of the test are listed in Table II.
  • the results of the two phases of the test are reproduced in the diagram in FIG. 1, in which the abscissa scale represents the equilibrium potential of the working electrode of the measurement cell, expressed in mV and the scale ordinate is a logarithmic scale of the intensity of the electric current in the working electrode expressed in ⁇ A per cm 2 of the immersed surface of the electrode.
  • the curve in unbroken lines reproduces the results of the first phase of the test and shows the unfavorable action of ferric ions on the corrosion of the electrode.
  • the dashed line reproduces the results of the second phase of the test: it shows, on the one hand, that the harmful influence of ferric ions is inhibited by additions of potassium ferrocyanide and, on the other hand, that the addition of potassium ferrocyanide decreases the equilibrium potential of the metal towards a fixed limit value.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Preventing Corrosion Or Incrustation Of Metals (AREA)
  • Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)

Abstract

The invention relates to a process for inhibiting the corrosion of an installation, made of a material chosen from amongst the metals which are less noble than hydrogen, and their alloys, in contact with an acid bath containing an alkylpyridinium chloride. A soluble cyanide complex, which is capable of forming an insoluble compound by reacting with ferric ions in the bath, is added to the bath so as to limit the concentration of the ferric ions in the bath to a maximum of 30 mg/kg. The content of ferric ions in the bath is controlled by means of a potentiometric measurement so as to bring the potential of the bath into the region of a predetermined value. The invention applies in particular to the treatment of baths for cleaning or descaling steel installations.

Description

La présente invention a pour objet un procédé pour inhiber la corrosion d'installations métalliques au contact d'un bain acide. Elle concerne plus particulièrement un procédé pour inhiber la corrosion, au contact de bains aqueux contenant un acide minéral, d'installations constituées de métaux moins nobles que l'hydrogène dans ces bains.The present invention relates to a method for inhibiting corrosion of metallic installations in contact with an acid bath. It relates more particularly to a process for inhibiting corrosion, in contact with aqueous baths containing a mineral acid, of installations made up of metals less noble than hydrogen in these baths.

Il est connu de traiter des installations métalliques avec des bains acides, notamment dans le but de les décaper ou de les désincruster. Ces techniques de décapage et de désincrustation sont d'exploitation courante dans l'industrie, où on les utilise notamment pour le détartrage des chaudières en acier et pour la désincrustation des réacteurs de cristallisation tels que les colonnes en acier ou en fonte utilisées pour la cristallisation de bicarbonate de sodium dans le procédé de fabrication de la soude à l'ammoniaque ou les évaporateurs en nickel utilisés pour la cristallisation de chlorure de sodium au départ de saumures ou de solutions aqueuses de chlorure de sodium et d'hydroxyde de sodium.It is known practice to treat metallic installations with acid baths, in particular with the aim of pickling or descaling them. These pickling and descaling techniques are widely used in the industry, where they are used in particular for the descaling of steel boilers and for the descaling of crystallization reactors such as the steel or cast iron columns used for crystallization of sodium bicarbonate in the process for the manufacture of soda with ammonia or the nickel evaporators used for the crystallization of sodium chloride from brines or aqueous solutions of sodium chloride and sodium hydroxide.

Les bains acides utilisés dans ces procédés de décapage et de désincrustation doivent généralement contenir un inhibiteur de corrosion dont le rôle est d'éviter une détérioration de l'installation sans nuire à l'action décapante ou désincrustante du bain.The acid baths used in these pickling and descaling processes must generally contain a corrosion inhibitor whose role is to avoid deterioration of the installation without harming the pickling or descaling action of the bath.

Les inhibiteurs de corrosion ajoutés aux bains acides ont aussi pour fonction d'éviter une corrosion des installations servant à leur manutention, notamment les cuves de stockage, les collecteurs et leurs accessoires tels que des vannes, des clapets et des pompes.Corrosion inhibitors added to acid baths also have the function of preventing corrosion of installations used for their handling, in particular storage tanks, manifolds and their accessories such as valves, valves and pumps.

Dans le cas particulier d'installations en acier ou en fonte, il est habituel d'utiliser du chlorure d'alkylpyridinium comme inhibiteur de corrosion. On a toutefois observé, en pratique, que malgré la présence de chlorure d'alkylpyridinium dans les bains acides, ceux-ci provoquent malgré tout, dans certains cas, une corrosion, parfois rapide de l'installation.In the particular case of steel or cast iron installations, it is usual to use alkylpyridinium chloride as a corrosion inhibitor. However, it has been observed, in practice, that despite the presence of alkylpyridinium chloride in the acid baths, these nevertheless cause, in some cases, corrosion, sometimes rapid, of the installation.

Un procédé connu pour remédier à cet inconvénient consiste à ajouter du chlorure stanneux au bain, en plus du chlorure d'alkyl- pyridinium.A known method for overcoming this drawback consists in adding stannous chloride to the bath, in addition to the alkylpyridinium chloride.

Ce procédé connu présente toutefois le désavantage de contaminer le bain par des ions d'étain, qui sont généralement considérés comme dangereux notamment lorsque l'évacuation des bains se fait dans des cours d'eau.However, this known method has the disadvantage of contaminating the bath with tin ions, which are generally considered to be dangerous, in particular when the baths are evacuated in watercourses.

Un autre procédé connu pour éliminer une pellicule d'oxyde à la surface des pièces en acier doux, consiste à les traiter avec une pâte de décapage constituée d'un mélange d'acide phosphorique, de ferrocyanure de potassium, d'urée, de phosphate de zinc, de sciure de bois, de mélasse et de chlorure de décylpyridinium (Chemical Abstracts, 1976, vol.85, n°97486d).Another known method for removing an oxide film on the surface of mild steel parts, consists in treating them with an etching paste made up of a mixture of phosphoric acid, potassium ferrocyanide, urea, phosphate. zinc, sawdust, molasses and decylpyridinium chloride (Chemical Abstracts, 1976, vol.85, no. 97486d).

L'utilisation d'une pâte pour le décapage d'installations industrielles pose toutefois de sérieuses difficultés, notamment dans le cas d'installations de grandes dimensions, ou lorsqu'il s'agit de traiter des zones difficilement accessibles de l'installation.The use of a paste for the pickling of industrial installations however poses serious difficulties, in particular in the case of large installations, or when it is a question of treating difficultly accessible zones of the installation.

L'invention vise à remédier aux inconvénients précités des procédés connus, en fournissant un procédé pour empêcher la corrosion d'installations métalliques au contact de bains acides contenant du chlorure d'alkylpyridinium, qui soit à la fois bon marché et inoffensif pour l'environnement.The invention aims to remedy the aforementioned drawbacks of known methods, by providing a method for preventing corrosion of metallic installations in contact with acid baths containing alkylpyridinium chloride, which is both inexpensive and harmless for the environment. .

L'invention concerne dès lors un procédé pour inhiber la corrosion au contact d'un bain aqueux contenant un acide minéral et du chlorure d'alkylpyridinium, d'une installation en métal moins noble que l'hydrogène dans ledit bain ou un alliage contenant un tel métal; selon l'invention, on ajoute au bain un complexe cyanuré soluble, capable de former un composé insoluble par réaction avec des ions ferriques du bain, le complexe cyanuré étant ajouté au bain en une quantité réglée entre celle nécessaire pour maintenir dans le bain, au contact de l'installation, une concentration en ions ferriques égale à 30 mg/kg et celle strictement nécessaire pour y obtenir une concentration nulle en ions ferriques.The invention therefore relates to a method for inhibiting corrosion in contact with an aqueous bath containing a mineral acid and alkylpyridinium chloride, from a metal installation less noble than hydrogen in said bath or an alloy containing such a metal; according to the invention, a soluble cyanide complex is added to the bath, capable of forming an insoluble compound by reaction with ferric ions of the bath, the cyanide complex being added to the bath in an amount adjusted between that necessary to maintain in the bath, at contact with the installation, a concentration of ferric ions equal to 30 mg / kg and that strictly necessary to obtain a zero concentration of ferric ions.

Dans le procédé selon l'invention, on entend désigner par l'expression"métal moins noble que l'hydrogène dans le bain",tout métal dont le potentiel d'équilibre dans le bain aqueux acide considéré est inférieur au potentiel d'équilibre de l'hydrogène dans le même bain et dans les mêmes conditions d'utilisation. En d'autres termes, il s'agit des métaux qui, en cas de corrosion au contact du bain, engendrent un dégagement d'hydrogène (Atlas d'équilibres électrochimiques - M. Pourbaix - Gauthier - Villars & Cie, Editeurs - 1963 - p.75 et 76). Le chrome, le fer, le cobalt, le nickel et le zinc sont des exemples de métaux qui entrent dans le cadre de l'invention. Par l'expression "alliage d'un tel métal", on entend désigner tous les alliages dont au moins un des éléments constitutifs est un métal moins noble que l'hydrogène, tel que défini plus haut. Elle désigne dès lors à la fois les alliages moins nobles que l'hydrogène (par exemple l'acier ordinaire et la fonte) et les alliages plus nobles que l'hydrogène (par exemple les cupronickels qui sont des alliages de nickel et de cuivre contenant de 70 à 85% de cuivre).In the process according to the invention, the expression “metal less noble than hydrogen in the bath” is intended to denote any metal whose equilibrium potential in the acidic aqueous bath considered is less than the equilibrium potential of hydrogen in the same bath and under the same conditions of use. In other words, these are metals which, in the event of corrosion in contact with the bath, generate hydrogen evolution (Atlas of electrochemical equilibria - M. Pourbaix - Gauthier - Villars & Cie, Editeurs - 1963 - p.75 and 76). Chromium, iron, cobalt, nickel and zinc are examples of metals which fall within the scope of the invention. By the expression "alloy of such a metal" is intended to denote all the alloys of which at least one of the constituent elements is a metal less noble than hydrogen, as defined above. It therefore designates both alloys less noble than hydrogen (for example ordinary steel and cast iron) and alloys more noble than hydrogen (for example cupronickels which are nickel and copper alloys containing from 70 to 85% copper).

Dans le procédé selon l'invention, le choix de l'acide minéral du bain n'est pas critique et dépend essentiellement de la nature du traitement. A titre d'exemple, dans le cas où le procédé est appliqué à l'élimination d'incrustations de carbonate de calcium des parois de l'installation, l'acide minéral est avantageusement de l'acide chlorhydrique, le bain consistant par exemple en une solution aqueuse contenant de 0,01 à 3 moles d'acide chlorhydrique par litre. Une solution normale d'acide chlorhydrique convient particulièrement bien comme bain pour le traitement d'installations en fer ou en alliage de fer.In the process according to the invention, the choice of mineral acid for the bath is not critical and essentially depends on the nature of the treatment. By way of example, in the case where the method is applied to the removal of calcium carbonate encrustations from the walls of the installation, the mineral acid is advantageously hydrochloric acid, the bath consisting for example of an aqueous solution containing 0.01 to 3 moles of hydrochloric acid per liter. Normal hydrochloric acid solution is suitable particularly suitable as a bath for the treatment of iron or iron alloy installations.

Le chlorure d'alkylpyridinium a pour fonction d'éviter une corrosion de l'installation par l'acide. Il est de préférence choisi parmi ceux dérivés d'alkanes possédant de 10 à 18 atomes de carbone. Le chlorure de cétyl-, de myristyl- et de laurylpyridi- uium se sont avérés particulièrement avantageux.The function of alkylpyridinium chloride is to prevent corrosion of the installation by acid. It is preferably chosen from those derived from alkanes having from 10 to 18 carbon atoms. Cetyl-, myristyl- and laurylpyridium chloride have been found to be particularly advantageous.

Toutes autres choses étant égales, dans le cas d'installations en acier ou en fonte, un mélange de chlorures d'alkylpyridinium contenant, à titre principal, du chlorure de laurylpyridinium et, en moindre quantités, du chlorure de myristylpyridinium et du chlorure de cétylpyridinium s'est révélé l'inhibiteur le plus actif.All other things being equal, in the case of steel or cast iron installations, a mixture of alkylpyridinium chlorides containing principally laurylpyridinium chloride and, in lesser amounts, myristylpyridinium chloride and cetylpyridinium chloride has been shown to be the most active inhibitor.

La teneur du bain en chlorure d'alkylpyridinium dépend de divers facteurs, notamment du choix de l'acide, de la concentration, du bain en cet acide, de la température du bain, de la nature du matériau de l'installation, de la durée du traitement de l'instal- lation avec le bain et du choix du chlorure d'alkylpyridinium. Elle peut être déterminée dans chaque cas particulier par un travail de routine au laboratoire.The content of alkylpyridinium chloride in the bath depends on various factors, in particular the choice of acid, the concentration, of the bath in this acid, the temperature of the bath, the nature of the material of the installation, the duration of treatment of the installa- ation with the bath and the choice of alkylpyridinium chloride. It can be determined in each particular case by routine laboratory work.

A titre d'exemple, dans le cas où le bain est une solution normale d'acide chlorhydrique, on obtient généralement de bons résultats en fixant la teneur en chlorure d'aikylpyridinium dans le bain entre 0,5 et 5000 mg/kg, de préférence entre 2 et 500 mg/kg. Les bains préférés pour le traitement d'installations en acier doux ou en fonte sont des solutions normales d'acide chlorhydrique contenant environ 75 à 200 mg de chlorure de laurylpyridinium par kg de solution.By way of example, in the case where the bath is a normal solution of hydrochloric acid, good results are generally obtained by fixing the content of aikylpyridinium chloride in the bath between 0.5 and 5000 mg / kg, preferably between 2 and 500 mg / kg. The preferred baths for the treatment of mild steel or cast iron installations are normal hydrochloric acid solutions containing approximately 75 to 200 mg of laurylpyridinium chloride per kg of solution.

Conformément à l'invention, on ajoute au bain un complexe cyanuré soluble, capable de réagir avec des ions ferriques du bain pour former un composé insoluble.According to the invention, a soluble cyanide complex is added to the bath, capable of reacting with ferric ions of the bath to form an insoluble compound.

Il a en effet été observé que la corrosion des installations métalliques par les bains acides contenant du chlorure d'alkylpyri- dinium semble être liée à la présence dans ceux-ci d'ions ferriques. Les ions ferriques du bain peuvent provenir de sources diverses. Ils peuvent notamment provenir de l'installation elle-même, lorsque celle-ci est en fer ou en alliage de fer, soit qu'ils résultent d'une corrosion de l'installation, soit qu'ils soient localisés dans une incrustation dissoute dans le bain dans le cas d'un traitement de désincrustation. Ces ions peuvent également être issus d'une corrosion locale d'un élément à base de fer, extérieur à l'installation proprement dite et avec lequel le bain est mis momentanément en contact. Cette possibilité peut notamment se présenter dans le cas où une installation en métal moins noble que l'hydrogène ou en un alliage contenant un tel métal, est soumise à un traitement de décapage ou de désincrustation au moyen d'un bain acide en provenance d'un circuit de manutention comprenant des éléments en acier ou en fonte subissant une corrosion locale.It has in fact been observed that corrosion of metallic installations by acid baths containing alkylpyridinium chloride seems to be linked to the presence in them of ferric ions. The ferric ions in the bath can come from various sources. They can in particular come from the installation itself, when the latter is made of iron or an iron alloy, either because they result from corrosion of the installation, or because they are located in an inlay dissolved in the bath in the case of a descaling treatment. These ions can also result from local corrosion of an iron-based element, external to the installation proper and with which the bath is brought into temporary contact. This possibility can in particular arise in the case where an installation made of a metal less noble than hydrogen or an alloy containing such a metal, is subjected to a pickling or descaling treatment by means of an acid bath coming from a handling circuit comprising steel or cast iron elements undergoing local corrosion.

Les complexes cyanurés constituent une classe de complexes chimiques très stables, bien connue en technique (Encyclopedia of Chemical Technology - Kirk & Othmer - The Interscience Encyclopedia, Inc. - 19 - Vol. 4, p. 677 à 680). Ils consistent en des anions complexes contenant au moins un atome métallique central lié par coordination à des groupements cyanurés.Cyanide complexes constitute a class of very stable chemical complexes, well known in the art (Encyclopedia of Chemical Technology - Kirk & Othmer - The Interscience Encyclopedia, Inc. - 19 - Vol. 4, p. 677 to 680). They consist of complex anions containing at least one central metallic atom linked by coordination to cyanide groups.

Selon l'invention, le complexe cyanuré doit être choisi parmi ceux qui sont solubles dans les bains aqueux acides et qui, par réaction avec les ions ferriques, forment des composés cyanurés insolubles.According to the invention, the cyanide complex must be chosen from those which are soluble in acidic aqueous baths and which, by reaction with ferric ions, form insoluble cyanide compounds.

Les complexes ferricyanure et ferrocyanure sont des exemples de complexes cyanurés qui conviennent bien dans le cadre de l'invention.The ferricyanide and ferrocyanide complexes are examples of cyanide complexes which are very suitable in the context of the invention.

Toutes autres choses étant égales, on préfère selon l'invention mettre en oeuvre des complexes cyanurés tétravalents, et plus particulièrement du ferrocyanure.All other things being equal, it is preferred according to the invention to use tetravalent cyanide complexes, and more particularly ferrocyanide.

Le complexe cyanuré peut être introduit dans le bain à l'état d'un composé hydrosoluble.The cyanide complex can be introduced into the bath in the form of a water-soluble compound.

Des composés hydrosolubles qui se sont avérés particulièrement avantageux, sont l'acide hexacyanoferrique et les ferrocyanures de calcium, d'ammonium, de sodium et de potassium, le ferrocyanure de potassium étant préféré.Water-soluble compounds which have been found to be particularly advantageous are hexacyanoferric acid and ferrocyanides of calcium, ammonium, sodium and potassium, potassium ferrocyanide being preferred.

Selon une caractéristique de l'invention, il convient de limiter l'addition de complexe cyanuré soluble, au maximum de la quantité strictement nécessaire pour réaliser une concentration nulle en ions ferriques dans le bain, au voisinage immédiat de l'installation.According to a characteristic of the invention, the addition of soluble cyanide complex should be limited to the maximum of the quantity strictly necessary to achieve a zero concentration of ferric ions in the bath, in the immediate vicinity of the installation.

L'expérience a en effet montré qu'un excès d'ions de ce complexe dans le bain avait pour résultat défavorable de nuire au caractère inhibiteur du chlorure d'alkylpyridinium et d'engendrer de la sorte une corrosion accélérée de l'installation.Experience has in fact shown that an excess of ions of this complex in the bath had the unfavorable result of harming the inhibitory nature of the alkylpyridinium chloride and thereby causing accelerated corrosion of the installation.

Il est généralement souhaitable, à titre de sécurité, de régler la quantité du complexe cyanuré ajoutée au bain, de telle manière que la teneur résiduelle en ions ferriques dans le bain au voisinage de l'installation, soit au moins égale à 0,1 mg/kg.It is generally desirable, for safety, to regulate the quantity of the cyanide complex added to the bath, so that the residual content of ferric ions in the bath in the vicinity of the installation is at least 0.1 mg / kg.

La quantité de ce complexe cyanuré soluble ajoutée au bain doit par ailleurs être suffisante pour maintenir la teneur résiduelle en ions ferriques dans le bain au voisinage de l'installation, à tout moment inférieure à une valeur critique à partir de laquelle leur influence sur la corrosion de l'installation devient inacceptable.The quantity of this soluble cyanide complex added to the bath must moreover be sufficient to maintain the residual content of ferric ions in the bath in the vicinity of the installation, at all times below a critical value from which their influence on corrosion of the installation becomes unacceptable.

Toutes autres choses étant égales, la fixation de la valeur critique susdite de la teneur résiduelle en ions ferriques dans le uain au voisinage de l'installation va dépendre d'un grand nombre de paramètres, tels que la nature du matériau de l'installation, la nature et la concentration de l'acide minéral dans le bain, la température du bain, la durée du traitement.All other things being equal, the fixing of the above critical value of the residual content of ferric ions in the uain in the vicinity of the installation will depend on a large number of parameters, such as the nature of the material of the installation, the nature and concentration of the mineral acid in the bath, the temperature of the bath, the duration of the treatment.

D'une manière générale, il convient dans la majorité des cas de régler l'addition du complexe cyanuré soluble pour que la teneur résiduelle en ions ferriques dans le bain au contact de l'installation, n'excède pas 30 mg/kg. Des valeurs qui conviennent bien pour la quantité de complexe cyanuré ajoutée au bain sont celles qui conduisent à l'obtention d'une teneur résiduelle en ions ferriques dans le bain au contact de l'installation,comprise entre 20 et 0,5 mg/kg, de préférence entre 5 et 1 mg/kg.In general, in most cases, the addition of the soluble cyanide complex should be adjusted so that the residual content of ferric ions in the bath in contact with the installation does not exceed 30 mg / kg. Values which are very suitable for the quantity of cyanide complex added to the bath are those which lead to obtaining a residual content of ferric ions in the bath in contact with the installation, of between 20 and 0.5 mg / kg , preferably between 5 and 1 mg / kg.

On peut faire usage de toute technique adéquate pour régler la quantité du complexe cyanuré ajoutée au bain.Any suitable technique can be used to control the amount of cyanide complex added to the bath.

Selon une forme d'exécution préférée de l'invention, on règle la quantité du complexe cyanuré soluble ajoutée au bain, par une mesure du potentiel du matériau de l'installation dans le bain.According to a preferred embodiment of the invention, the quantity of soluble cyanide complex added to the bath is adjusted by measuring the potential of the material of the installation in the bath.

On a en effet observé que, pour une composition déterminée du bain et un matériau défini de l'installation, la grandeur du potentiel du matériau de l'installation dans le bain est une mesure de sa teneur en ions ferriques.It has in fact been observed that, for a determined composition of the bath and a defined material of the installation, the magnitude of the potential of the material of the installation in the bath is a measure of its ferric ion content.

Il suffit dès lors, pendant le traitement de l'installation, de régler l'addition du complexe cyanuré soluble dans le bain, de manière à maintenir le potentiel du matériau de l'installation au contact du bain en permanence entre deux valeurs critiques prédéterminées, correspondant respectivement aux valeurs extrêmes tolérées des ions ferriques dans le bain, au contact de l'installation. La détermination de ces valeurs critiques du potentiel peut être réalisée facilement par un travail de routine au laboratoire reproduisant les conditions envisagées pour le traitement de l'installation.It is therefore sufficient, during the treatment of the installation, to regulate the addition of the cyanide complex soluble in the bath, so as to maintain the potential of the material of the installation in permanent contact with the bath between two predetermined critical values, corresponding respectively to the extreme tolerated values of ferric ions in the bath, in contact with the installation. The determination of these critical potential values can be easily carried out by routine laboratory work reproducing the conditions envisaged for the treatment of the installation.

On a par ailleurs observé qu'une diminution progressive de la teneur en ions ferriques dans le bain au contact du matériau de l'installation conduit à une diminution progressive du potentiel de ce matériau jusqu'à une valeur fixe, correspondant à une teneur nulle en ions ferriques dans le bain au contact du matériau; d'autre part, une addition excédentaire du complexe cyanuré soluble par rapport à celle qui est strictement nécessaire pour annuler la teneur en ions ferriques dans le bain, au contact du matériau de l'installation, n'exerce aucune influence sur la valeur du potentiel de ce matériau, qui conserve dès lors la valeur fixe précitée. Cette valeur fixe du potentiel peut évidemment être déterminée aisément par un travail de routine au laboratoire de sorte que, selon une forme de réalisation avantageuse de l'invention, il suffit de régler l'addition du complexe dans le bain de manière à maintenir le potentiel du matériau de l'installation en permanence au voisinage de cette valeur fixe.It has also been observed that a gradual decrease in the content of ferric ions in the bath in contact with the material of the installation leads to a progressive decrease in the potential of this material up to a fixed value, corresponding to a zero content ferric ions in the bath in contact with the material; on the other hand, an excess addition of the soluble cyanide complex compared to that which is strictly necessary to cancel the content of ferric ions in the bath, in contact with the material of the installation, has no influence on the value of the potential of this material, which therefore retains the above-mentioned fixed value. This fixed value of the potential can obviously be easily determined by routine laboratory work so that, according to an advantageous embodiment of the invention, it suffices to regulate the addition of the complex to the bath so as to maintain the potential. of the material of the installation permanently in the vicinity of this fixed value.

La méthode utilisée pour mesurer le potentiel du matériau de l'installation dans le bain n'est pas critique. On peut par exemple utiliser à cet effet une cellule de mesure électrochimique comprenant une électrode de référence (par exemple une électrode à hydrogène ou une électrode au calomel) et une électrode de travail exécutée dans le même matériau que l'installation et immergée dans le bain au voisinage immédiat de l'installation.The method used to measure the potential of the installation material in the bath is not critical. One can for example use for this purpose an electrochemical measuring cell comprising a reference electrode (for example a hydrogen electrode or a calomel electrode) and a working electrode executed in the same material as the installation and immersed in the bath in the immediate vicinity of the installation.

L'électrode de travail peut être un barreau métallique, par exemple, un barreau cylindrique. On préfère toutefois, selon une forme d'exécution particulière de l'invention, utiliser à titre d'électrode de travail, une zone de l'installation qui est en contact avec le bain, par exemple la paroi d'une cuve, d'une canalisation, le clapet d'obturation d'une vanne ou encore la roue ou la volute d'une pompe.The working electrode can be a metal bar, for example, a cylindrical bar. However, it is preferred, according to a particular embodiment of the invention, to use as working electrode, an area of the installation which is in contact with the bath, for example the wall of a tank, a pipe, the shutter valve of a valve or the impeller or volute of a pump.

Le procédé selon l'invention trouve une application intéressante pour la désincrustation des évaporateurs en nickel ou en alliage de nickel utilisés pour cristalliser du chlorure de sodium au départ de saumures caustiques produites par électrolyse d'une saumure de chlorure de sodium dans une cellule d'électrolyse à diaphragme perméable. Une autre application intéressante du procédé selon l'invention réside dans la désincrustation de la zone de réfrigération des colonnes servant à la cristallation du bicarbonate de sodium dans le procédé de fabrication de la soude à l'ammoniaque (Manufacture of soda -Te-Pang Hou - Hafner Publishing Co - 1969).The method according to the invention finds an interesting application for the descaling of evaporators made of nickel or of nickel alloy used to crystallize sodium chloride from caustic brines produced by electrolysis of a sodium chloride brine in a cell. permeable diaphragm electrolysis. Another interesting application of the process according to the invention lies in the descaling of the refrigeration zone of the columns used for the crystallization of sodium bicarbonate in the process for the manufacture of soda with ammonia (Manufacture of soda -Te-Pang Hou - Hafner Publishing Co - 1969).

Le procédé selon l'invention peut également s'appliquer à la manutention d'acides minéraux en solution aqueuse, dans des canalisations ou des réservoirs métalliques.The method according to the invention can also be applied to the handling of mineral acids in aqueous solution, in metal pipes or tanks.

Dans le cas particulier où le matériau de l'installation est un alliage comportant à la fois un métal moins noble que l'hydrogène, tel que défini plus haut, et un métal plus noble que l'hydrogène, il peut s'avérer souhaitable d'ajouter au bain, en plus du chlorure d'alkylpyridinium et du complexe cyanuré, une substance connue en soi pour inhiber la corrosion des métaux plus nobles que l'hydrogène par les bains aqueux acides.In the particular case where the material of the installation is an alloy comprising both a metal less noble than hydrogen, as defined above, and a metal more noble than hydrogen, it may prove desirable to add to the bath, in addition to the alkylpyridinium chloride and the cyanide complex, a substance known per se to inhibit corrosion of metals nobler than hydrogen by acidic aqueous baths.

L'iodure de potassium s'avère une substance préférée pour inhiber la corrosion de tels métaux.Potassium iodide is a preferred substance for inhibiting corrosion of such metals.

Des exemples d'alliages pour lesquels il est opportun d'ajouter un tel inhibiteur de corrosion aux bains aqueux acides sont les cupronickels qui sont des alliages de nickel et de cuivre contenant généralement de 70 à 85% de cuivre et de 15 à 30% de nickel (Traité de Métallurgie Structurale - A. De Sy et J. Vidts - Dunod - 1962 - p.184).Examples of alloys for which it is expedient to add such a corrosion inhibitor to acidic aqueous baths are cupronickels which are nickel and copper alloys generally containing from 70 to 85% of copper and from 15 to 30% of nickel (Treaty of Structural Metallurgy - A. De Sy and J. Vidts - Dunod - 1962 - p.184).

L'intérêt de l'invention va apparaître au cours de la description suivante de quelques exemples d'application en référence aux dessins annexés, qui sont trois diagrammes reproduisant respectivement les résultats des essais décrits aux exemples.The advantage of the invention will appear during the following description of a few application examples with reference to the appended drawings, which are three diagrams respectively reproducing the results of the tests described in the examples.

Dans chacun des exemples d'application qui vont suivre, on a d'abord examiné l'influence que la présence des ions ferriques dans un bain d'acide chlorhydrique contenant du chlorure de laurylpyridinium exerce sur la corrosion d'un matériau métallique choisi. On a ensuite examiné l'influence bénéfique que l'addition de ferrocyanure de potassium dans un tel bain exerce sur la protection du matériau contre la corrosion.In each of the application examples which follow, we first examined the influence which the presence of ferric ions in a hydrochloric acid bath containing laurylpyridinium chloride exerts on the corrosion of a chosen metallic material. We then examined the beneficial influence which the addition of potassium ferrocyanide in such a bath exerts on the protection of the material against corrosion.

A cet effet, on a utilisé une cellule de mesure électrochimique comprenant une électrode de travail, exécutée dans le matériau étudié et immergée dans une solution aqueuse normale d'acide chlorhydrique, contenant, par kg, 100 mg du produit connu sous le nom "Dehyquart C" (Henkel Int. GmbH) qui consiste principalement en du chlorure de laurylpyridinium.For this purpose, an electrochemical measuring cell was used comprising a working electrode, executed in the material studied and immersed in a normal aqueous solution of hydrochloric acid, containing, per kg, 100 mg of the product known under the name "Dehyquart C "(Henkel Int. GmbH) which consists mainly of laurylpyridinium chloride.

L'électrode de travail consistait en un barreau cylindrique dont la surface en contact avec le bain avait une aire égale à 10 cm2.The working electrode consisted of a cylindrical bar whose surface in contact with the bath had an area equal to 10 cm 2 .

Exemple 1Example 1

L'essai a été exécuté avec une électrode de travail en acier ordinaire.The test was carried out with an ordinary steel working electrode.

Au cours d'une première phase de l'essai, on a procédé à cinq additions consécutives de chlorure ferrique hexahydraté dans la solution de la cellule de mesure. Les additions consécutives de chlorure ferrique ont été réglées pour amener la teneur en ions ferriques dans la solution successivement également à 10, 30, 100, 300 et 1000 mg/kg.During a first phase of the test, five consecutive additions of ferric chloride hexahydrate were made to the solution of the measuring cell. Consecutive ferric chloride additions have been adjusted to bring the ion content ferric in the solution successively also at 10, 30, 100, 300 and 1000 mg / kg.

A l'issue de chaque addition de chlorure ferrique, on a mesuré, par une méthode potentiométrique, d'une part l'intensité du courant dans l'électrode qui est une mesure de sa vitesse de corrosion, et, d'autre part, le potentiel d'équilibre de l'électrode dans le bain, par rapport à l'électrode de référence au calomel, saturée en KCl. Les résultats sont consignés au tableau I ci-dessous.

Figure imgb0001
At the end of each addition of ferric chloride, the intensity of the current in the electrode, which is a measure of its corrosion rate, was measured, on the one hand, and, on the other hand, the equilibrium potential of the electrode in the bath, relative to the reference electrode to the calomel, saturated with KCl. The results are reported in Table I below.
Figure imgb0001

A l'issue de la première phase de l'essai, on a entamé immédiatement la seconde phase de l'essai, au cours de laquelle on a procédé à cinq additions consécutives de ferrocyanure de potassium trihydraté dans la solution de la cellule de mesure. Les additions consécutives de ferrocyanure de potassium ont été réglées de manière que sa teneur résiduelle en ions ferriques soit ramenée successivement à 300, 100, 30, 10 et 0 mg/kg. Les résultats de cette seconde phase de l'essai sont mentionnés au tableau II.

Figure imgb0002
At the end of the first phase of the test, the second phase of the test was immediately started, during which five consecutive additions of potassium ferrocyanide trihydrate were made to the solution of the measuring cell. The consecutive additions of potassium ferrocyanide were adjusted so that its residual content of ferric ions was successively reduced to 300, 100, 30, 10 and 0 mg / kg. The results of this second phase of the test are listed in Table II.
Figure imgb0002

Les résultats des deux phases de l'essai sont reproduits au diagramme de la figure 1, dans lequel l'échelle des abscisses représente le potentiel d'équilibre de l'électrode de travail de la cellule de mesure, exprimé en mV et l'échelle des ordonnées est une échelle logarithmique de l'intensité du courant électrique dans l'électrode de travail exprimée en µA par cm2 de la surface immergée de l'électrode. La courbe en trait ininterrompu reproduit les résultats de la première phase de l'essai et montre l'action défavorable des ions ferriques sur la corrosion de l'électrode. La courbe en trait interrompu reproduit les résultats de la seconde phase de l'essai : elle montre, d'une part, que l'influence nuisible des ions ferriques est inhibée par des additions de ferrocyanure de potassium et, d'autre part, que l'addition du ferrocyanure de potassium fait décroître le potentiel d'équilibre du métal vers une valeur limite fixe.The results of the two phases of the test are reproduced in the diagram in FIG. 1, in which the abscissa scale represents the equilibrium potential of the working electrode of the measurement cell, expressed in mV and the scale ordinate is a logarithmic scale of the intensity of the electric current in the working electrode expressed in µA per cm 2 of the immersed surface of the electrode. The curve in unbroken lines reproduces the results of the first phase of the test and shows the unfavorable action of ferric ions on the corrosion of the electrode. The dashed line reproduces the results of the second phase of the test: it shows, on the one hand, that the harmful influence of ferric ions is inhibited by additions of potassium ferrocyanide and, on the other hand, that the addition of potassium ferrocyanide decreases the equilibrium potential of the metal towards a fixed limit value.

Exemple 2Example 2

On a répété les deux phases de l'essai de l'exemple 1 avec une électrode de travail en acier de nuance 316 L (normes A.S.T.M.) qui est un acier inoxydable austénitique de composition pondérale suivante (Techniques de l'Ingénieur - Métallurgie -Vol. I - Form. M 323 - 17 -1974) :

  • C : max. 0,03%
  • Mn : max. 2,0%
  • Si : max. 1,0%
  • P : max. 0,045%
  • S : max. 0,030%
  • Cr : 16,0-18,8%
  • Ni : 10,0-14,0%
  • Mo : 2,0- 3,0%
The two phases of the test of Example 1 were repeated with a working electrode of steel grade 316 L (ASTM standards) which is an austenitic stainless steel with the following weight composition (Engineering Techniques - Metallurgy - Flight I - Form M 323 - 17 -1974):
  • C: max. 0.03%
  • Mn: max. 2.0%
  • If: max. 1.0%
  • P: max. 0.045%
  • S: max. 0.030%
  • Cr: 16.0-18.8%
  • Ni: 10.0-14.0%
  • MB: 2.0- 3.0%

Les résultats des deux phases de l'essai sont consignés aux 10 tableaux III et IV et reportés sur le diagramme de la figure 2.

Figure imgb0003
Figure imgb0004
 The results of the two phases of the test are recorded in Tables III and IV and plotted on the diagram in Figure 2.
Figure imgb0003
Figure imgb0004

Exemple 3Example 3

Les deux phases successives de l'essai de l'exemple 1, ont été répétées en utilisant cette fois des électrodes de travail en alliage connu sous le nom Monel 400 (Huntington Alloy Products Division et International Nickel Company Inc.) qui est un alliage de nickel et de cuivre ayant la composition pondérale suivante (Rompps Chemie - Lexikon, 1974) :

  • Ni (+Co) : > 63%
  • Mn : 2%
  • C : 0,3%
  • Fe : 2,5%
  • S : 0,024%
  • Si : 0,5%
  • Cu : solde
The two successive phases of the test of Example 1 were repeated, this time using working electrodes of an alloy known under the name Monel 400 (Huntington Alloy Products Division and International Nickel Company Inc.) which is an alloy of nickel and copper having the following weight composition (Rompps Chemie - Lexikon, 1974):
  • Ni (+ Co):> 63%
  • Mn: 2%
  • C: 0.3%
  • Fe: 2.5%
  • S: 0.024%
  • If: 0.5%
  • Cu: balance

Les résultats des deux phases de l'essai sont consignés respectivement aux tableaux V et VI et reportés sur le diagramme de la figure 3.

Figure imgb0005
Figure imgb0006
 The results of the two phases of the test are reported in Tables V and VI respectively and shown in the diagram in Figure 3.
Figure imgb0005
Figure imgb0006

Claims (10)

1 - Procédé pour inhiber la corrosion au contact d'un bain aqueux contenant un acide minéral et du chlorure d'alkylpyridinium d'une installation en un métal moins noble que l'hydrogène dans le bain ou en alliage contenant un tel métal, caractérisé en ce qu'on ajoute au bain un complexe cyanuré soluble capable de former un composé insoluble par réaction avec des ions ferriques du bain, le complexe cyanuré étant ajouté au bain en une quantité réglée entre celle nécessaire pour maintenir dans le bain au contact de l'installation une concentration en ions ferriques égale à 30 mg/kg et .-elle strictement nécessaire pour y obtenir une concentration nulle en ions ferriques.1 - Process for inhibiting corrosion on contact with an aqueous bath containing a mineral acid and alkylpyridinium chloride of an installation made of a metal less noble than hydrogen in the bath or of an alloy containing such a metal, characterized in adding to the bath a soluble cyanide complex capable of forming an insoluble compound by reaction with ferric ions of the bath, the cyanide complex being added to the bath in an amount adjusted between that necessary to keep in the bath in contact with the installation a concentration of ferric ions equal to 30 mg / kg and. it strictly necessary to obtain a zero concentration of ferric ions there. 2 - Procédé selon la revendication 1, caractérisé en ce qu'on met en oeuvre un complexe cyanuré soluble qui est tétravalent.2 - Process according to claim 1, characterized in that a soluble cyanide complex which is tetravalent is used. 3 - Procédé selon la revendication 2, caractérisé en ce qu'on met en oeuvre du ferrocyanure.3 - Process according to claim 2, characterized in that ferrocyanide is used. 4 - Procédé selon la revendication 3, caractérisé en ce que le complexe ferrocyanure est ajouté au bain à l'état de ferrocyanure de potassium.4 - Process according to claim 3, characterized in that the ferrocyanide complex is added to the bath in the form of potassium ferrocyanide. 5 - Procédé selon l'une quelconque des revendications 1 à 4, caractérisé en ce qu'on règle la quantité du complexe cyanuré soluble ajoutée au bain en sorte d'y maintenir la concentration en ions ferriques comprise entre 5 et 1 mg/kg.5 - Process according to any one of claims 1 to 4, characterized in that the quantity of the soluble cyanide complex added to the bath is adjusted so as to maintain the concentration of ferric ions therein between 5 and 1 mg / kg. 6 - Procédé selon l'une quelconque des revendications 1 à 4, caractérisé en ce qu'on règle la quantité de complexe cyanuré soluble ajoutée au bain par une mesure du potentiel du matériau de l'installation.6 - Process according to any one of claims 1 to 4, characterized in that the quantity of soluble cyanide complex added to the bath is adjusted by a measurement of the potential of the material of the installation. 7 - Procédé selon l'une quelconque des revendications 1 à 6, caractérisé en ce que l'on met en oeuvre comme acide minéral de l'acide chlorhydrique.7 - Process according to any one of claims 1 to 6, characterized in that hydrochloric acid is used as the mineral acid. 8 - Procédé selon la revendication 7, caractérisé en ce que l'on utilise comme bain une solution normale d'acide chlorhydrique contenant de 75 à 200 mg de chlorure d'alkylpyridinium.8 - Process according to claim 7, characterized in that a normal solution of hydrochloric acid containing from 75 to 200 mg of alkylpyridinium chloride is used as the bath. 9 - Procédé selon l'une quelconque des revendications 1 à 8, caractérisé en ce que le chlorure d'alkylpyridinium est choisi parmi ceux dérivés d'alkanes possédant de 12 à 18 atomes de carbone.9 - Process according to any one of claims 1 to 8, characterized in that the alkylpyridinium chloride is chosen from those derived from alkanes having from 12 to 18 carbon atoms. 10 - Procédé selon l'une quelconque des revendications 1 à 9, caractérisé en ce que l'installation comporte du chrome, du zinc, du fer, du cobalt, du nickel ou un alliage de ces métaux.10 - Process according to any one of claims 1 to 9, characterized in that the installation comprises chromium, zinc, iron, cobalt, nickel or an alloy of these metals.
EP80200835A 1979-09-17 1980-09-05 Process for inhibiting the corrosion of a metallic installation upon contact with an acidic bath Expired EP0025624B1 (en)

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AT80200835T ATE3782T1 (en) 1979-09-17 1980-09-05 METHOD OF INHIBITING CORROSION WHEN CONTACT WITH AN ACID BATH FOR A METALLIC PLANT.

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FR7923283A FR2465010A1 (en) 1979-09-17 1979-09-17 PROCESS FOR INHIBITING THE CORROSION OF A METAL PLANT IN CONTACT WITH AN ACIDIC BATH
FR7923283 1979-09-17

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EP0025624A1 true EP0025624A1 (en) 1981-03-25
EP0025624B1 EP0025624B1 (en) 1983-06-15

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EP80200835A Expired EP0025624B1 (en) 1979-09-17 1980-09-05 Process for inhibiting the corrosion of a metallic installation upon contact with an acidic bath

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US (1) US4402759A (en)
EP (1) EP0025624B1 (en)
AT (1) ATE3782T1 (en)
DE (1) DE3063776D1 (en)
FR (1) FR2465010A1 (en)

Cited By (3)

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Publication number Priority date Publication date Assignee Title
EP0193239A1 (en) * 1985-03-04 1986-09-03 SOLVAY & Cie (Société Anonyme) Compositions and process for chemically polishing steel surfaces
FR2582675A1 (en) * 1985-06-03 1986-12-05 Solvay BATHS AND METHODS FOR CHEMICAL POLISHING OF STAINLESS STEEL SURFACES
RU2450497C2 (en) * 2010-05-13 2012-05-20 Федеральное государственное образовательное учреждение высшего профессионального образования Российский Государственный аграрный университет - Московская сельскохозяйственная академия имени К.А. Тимирязева (ФГОУ ВПО РГАУ - МСХА имени К.А. Тимирязева) Device for loosening tillage

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0032416B2 (en) * 1980-01-08 1987-06-16 Central Electricity Generating Board Descaling process
WO2017112721A1 (en) * 2015-12-22 2017-06-29 Albemarle Corporation Corrosion inhibitors and related processes for their production and use

Citations (3)

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FR1037300A (en) * 1950-10-27 1953-09-15 Henkel & Cie Gmbh Method and agents for the protection of iron against attack by acidic liquids
FR1182531A (en) * 1957-09-10 1959-06-25 Poor & Co Process for the acid pickling of metals and products used for the implementation of this process
DE1517569A1 (en) * 1962-12-21 1969-08-21 T E B Sa Method of inhibiting the corrosive effects of water with low hardness

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US2831814A (en) * 1951-12-19 1958-04-22 Poor & Co Acid pickling of metals and compositions therefor
NL155315B (en) * 1964-06-09 1977-12-15 Ver Kunstmestfabriekn Mekog Al PROCEDURE FOR CLEANING IRONS OR STEEL, INTERNAL SURFACES OF INDUSTRIAL EQUIPMENT

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FR1037300A (en) * 1950-10-27 1953-09-15 Henkel & Cie Gmbh Method and agents for the protection of iron against attack by acidic liquids
FR1182531A (en) * 1957-09-10 1959-06-25 Poor & Co Process for the acid pickling of metals and products used for the implementation of this process
DE1517569A1 (en) * 1962-12-21 1969-08-21 T E B Sa Method of inhibiting the corrosive effects of water with low hardness

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CHEMICAL ABSTRACTS, vol. 85, 1976 page 205, réf. 97486d Columbus, Ohio, US V.S. KOTSUR et al.: "Paste for removing corrosion products from the surface of carbon steels" & Khim. Neft. Mashinostr. 1976,(4), 23-4 *

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0193239A1 (en) * 1985-03-04 1986-09-03 SOLVAY & Cie (Société Anonyme) Compositions and process for chemically polishing steel surfaces
FR2578271A1 (en) * 1985-03-04 1986-09-05 Solvay BATHS AND PROCESS FOR THE CHEMICAL POLISHING OF STEEL SURFACES.
US4652340A (en) * 1985-03-04 1987-03-24 Solvay & Cie (Societe Anonyme) Baths and process for the chemical polishing of steel surfaces
FR2582675A1 (en) * 1985-06-03 1986-12-05 Solvay BATHS AND METHODS FOR CHEMICAL POLISHING OF STAINLESS STEEL SURFACES
EP0206386A1 (en) * 1985-06-03 1986-12-30 SOLVAY & Cie (Société Anonyme) Baths and process for chemically polishing stainless-steel surfaces
US4678541A (en) * 1985-06-03 1987-07-07 Solvay & Cie. (Societe Anonyme) Baths and process for chemical polishing of stainless steel surfaces
RU2450497C2 (en) * 2010-05-13 2012-05-20 Федеральное государственное образовательное учреждение высшего профессионального образования Российский Государственный аграрный университет - Московская сельскохозяйственная академия имени К.А. Тимирязева (ФГОУ ВПО РГАУ - МСХА имени К.А. Тимирязева) Device for loosening tillage

Also Published As

Publication number Publication date
FR2465010B1 (en) 1982-10-08
ATE3782T1 (en) 1983-06-15
FR2465010A1 (en) 1981-03-20
US4402759A (en) 1983-09-06
EP0025624B1 (en) 1983-06-15
DE3063776D1 (en) 1983-07-21

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