EP0162491B1 - Process for inhibiting corrosion of a metallic mass in contact with an acidic bath containing ferric ions - Google Patents

Process for inhibiting corrosion of a metallic mass in contact with an acidic bath containing ferric ions Download PDF

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Publication number
EP0162491B1
EP0162491B1 EP85200527A EP85200527A EP0162491B1 EP 0162491 B1 EP0162491 B1 EP 0162491B1 EP 85200527 A EP85200527 A EP 85200527A EP 85200527 A EP85200527 A EP 85200527A EP 0162491 B1 EP0162491 B1 EP 0162491B1
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EP
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Prior art keywords
bath
stack
process according
ferric ions
felts
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EP85200527A
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German (de)
French (fr)
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EP0162491A1 (en
Inventor
Daniel Tytgat
Pierre Lefèvre
Dominique Balthasart
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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
    • C23F15/00—Other methods of preventing corrosion or incrustation
    • 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

Definitions

  • the present invention relates to a method for inhibiting the corrosion of metallic masses in contact with acid baths containing ferric ions, for example an industrial installation subjected to a descaling operation, or metallurgical products subjected to a pickling operation.
  • Corrosion inhibitors commonly used for this purpose are alkylpyridinium chlorides, hexamethylenetetramine and organic compounds comprising sulfonium groups.
  • corrosion inhibitors in the acid baths, these nonetheless cause rapid corrosion of the treated metallic masses. This corrosion would be due to the presence of oxidants in the bath mainly ferric ions.
  • reducing agents for example stannous chloride, in addition to corrosion inhibitors.
  • reducers in the bath is generally expensive, especially in the case of non-deaerated baths because there is then an appreciable loss in reducers, due to their untimely consumption by the oxygen of the bath, this consumption being all the more important. that the temperature is higher. It also results in an increase in the contamination of the bath by reducing agents, some of which, in particular stannous ions, are generally considered dangerous for the ecology, in particular when the residual baths are discharged into lakes or watercourses. .
  • the invention aims to remedy the aforementioned drawbacks by providing a method for inhibiting corrosion of metallic masses in contact with acid baths containing ferric ions, which is reliable, economical and harmless for the environment.
  • the invention therefore relates to a method for inhibiting corrosion of a metallic mass in contact with an acid bath containing ferric ions; according to the invention, at least part of the bath is circulated through a stack of non-graphitic carbon or graphite felts, alternating with solid bodies of iron or an iron alloy.
  • the method according to the invention applies to any acid bath containing ferric ions, capable of causing an electrochemical oxidation of the metal mass under the conditions of use of the bath.
  • the ferric ions present in the bath can come from very diverse sources such as, for example, from oxidized layers on the surface of the metallic mass, from corrosion of the bath handling circuit, from incrustation on the surface of the metallic mass, of impurities present in the acid bath; in the case of aqueous acid baths, ferric ions can sometimes be provided by the water used for the preparation of the bath.
  • a fraction of the bath is periodically removed and it is circulated through the stack for a predetermined time sufficient to reduce at least part of the ferric ions which it contains; the fraction is then returned to the bath.
  • a second treatment method which is preferred, the entire bath is circulated through the packing, at a rate adjusted so that at the exit of the stack, its ferric ion content has fallen below d 'a predetermined value.
  • the bath can be circulated through the stack periodically or continuously.
  • the treatment of the bath in the stack is generally governed, so that the residual quantity of ferric ions in the bath in contact with the metallic mass does not exceed 300 mg / 1, preferably 200 mg / 1. Residual contents not exceeding 150 mg / I are recommended, especially those between 1 and 100 mg / I.
  • a stack is used in which the felts are formed of fibers whose diameter does not exceed 25 microns, preferably 15 microns. It is preferred to use stacks of mild steel bodies and non-graphitic carbon felts, the fiber diameter of which is between 8 and 12 microns.
  • the solid bodies of the stack can have any profile allowing a large contact surface with the felts.
  • a stack is used in which the solid bodies of iron or of iron alloy are plates which alternate with carbon or graphite felts.
  • a stack is used in which the solid bodies are perforated plates and the bath is circulated through the stack, in a direction transverse to the plates and the felts.
  • the bath is circulated through the stack, in a direction transverse to the plates and the felts.
  • the method according to the invention also applies to acid baths containing a corrosion inhibitor.
  • a corrosion inhibitor may be, for example, alkylpyridinium chloride which is advantageously selected from those derived from alkanes having from 10 to 18 carbon atoms.
  • alkylpyridinium chloride which is advantageously selected from those derived from alkanes having from 10 to 18 carbon atoms.
  • cetyl-, myristil- or laurylpyridinium chloride in an amount regulated between 0.5 and 5000 mg per kg of the bath, preferably between 2 and 500 mg / kg.
  • corrosion inhibitors which can be used in the baths treated by the process according to the invention are hexamethylenetetramine and formalin.
  • the method according to the invention applies to any metallic mass treated in an acid bath containing ferric ions capable of attacking the metallic mass. It applies in particular to metallic masses comprising iron, chromium, zinc, cobalt, nickel or an alloy containing at least one of these metals. It finds a particularly interesting application in the case of metallic masses treated with aqueous baths of mineral acid containing ferric ions. It is particularly applicable to descaling, by means of such baths, of nickel or nickel alloy evaporators used to crystallize sodium chloride from caustic brines produced by electrolysis of sodium chloride brine in a cell. permeable diaphragm electrolysis.
  • the acid bath can for example be an aqueous solution of sulfuric acid or hydrochloric acid.
  • Aqueous solutions containing from 0.01 to 6 moles of hydrochloric acid per liter are generally suitable.
  • the installation shown diagrammatically in FIG. 1 comprises a pickling tank 1, containing a mass of ordinary steel or cast iron 2 to be pickled. This consists, for example, of a stack of coils of drawn wires or of strips.
  • the pickling is carried out by means of a bath 3 consisting of a normal hydrochloric acid solution.
  • the pickling tank is connected, by means of a pump 4 and pipes 5 and 6, to a treatment cell 7.
  • a treatment cell 7 This is formed (fig. 2) of a vertical tubular chamber 8 containing a stack of perforated horizontal steel discs 9, alternating with horizontal felt 10 made of non-graphitic carbon fibers.
  • the discs 9 are crossed by tubular vertical perforations 11.
  • the bath 3 is circulated from the tank 1 to the cell 7, via the pipes 5 and 6 and the pump 4.
  • the circulation of the bath 3 in the cell 7 can be carried out periodically or continuously.
  • the bath circulates in the perforations 11 in contact with the discs 9 and through the felts 10, and the ferric ions are reduced to ferrous ions.
  • an electrochemical measuring cell comprising a rotating platinum electrode and a fixed platinum counter electrode, immersed in the hydrochloric acid bath, and a calomel reference electrode, saturated with KCI ; by means of a potentiostatic circuit, the rotating electrode was maintained at a constant potential of - 150 mV relative to the reference electrode and the intensity of the electric current in the measuring cell was measured, which is substantially proportional to the concentration of ferric ions.
  • the abscissa scale indicates the time, in minutes, and the ordinate scale indicates the concentration of the bath in ferric ions, expressed in g / I.
  • the stack consisted of thirteen cast iron discs alternating with polyvinyl chloride rings.
  • the flow rate of the solution through the stack was 150 l / h.
  • the results of the test are reproduced on the curve (12) of the diagram in FIG. 3.
  • Example 5 a stack of perforated steel discs (of area equal to 20 cm 2) was used alternating with graphite felts.
  • the number of graphite felts was 6 in Example 3 and 12 in Example 4, respectively.
  • Example 5 two stacks of 13 discs (and 12 felts) were used, the two stacks being mounted in bypass on the hydrochloric acid solution circuit.
  • the flow rate of the solution was 200 l / h in each test.
  • Example 8 The conditions of Example 8 were repeated, using two identical stacks (13 steel discs and twelve carbon felts) arranged in parallel in the solution circuit. The results of the test are reproduced by the curve (20) of the diagram of FIG. 5. It is observed there that 8 minutes are sufficient to bring the content of ferric ions in the bath, from 10 g / 1 to 0.1 g / 1 .

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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)
  • Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
  • Preventing Corrosion Or Incrustation Of Metals (AREA)
  • Cosmetics (AREA)

Abstract

Process for inhibiting the corrosion of a mass of metal (2) in contact with an acid bath (3) containing ferric ions, according to which at least a part of the bath (3) is circulated through a stack of felts (10) made of carbon or graphite, alternating with perforated plates made of iron or an iron alloy (9). The process applies to the pickling of metallurgical products made of steel in hydrochloric acid baths.

Description

La présente invention est relative à un procédé pour inhiber la corrosion de masses métalliques au contact de bains acides contenant des ions ferriques par exemple une installation industrielle soumise à une opération de désincrustation, ou des produits métallurgiques soumis à une opération de décapage.The present invention relates to a method for inhibiting the corrosion of metallic masses in contact with acid baths containing ferric ions, for example an industrial installation subjected to a descaling operation, or metallurgical products subjected to a pickling operation.

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.It is known practice to treat metal 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 sodium bicarbonate in the process for making ammonia soda.

Il est par ailleurs de pratique courante, dans l'élaboration des produits métallurgiques, de soumettre ceux-ci à une opération finale de décapage dans un bain acide. C'est principalement le cas des produits de laminage en acier ordinaire, et plus spécialement de ceux issus du laminage à froid tels que les feuillards et les fils tréfilés.It is also common practice, in the production of metallurgical products, to subject them to a final pickling operation in an acid bath. This is mainly the case for ordinary steel rolling products, and more particularly for those produced by cold rolling such as strip and drawn wire.

Il est de pratique courante d'incorporer des inhibiteurs de corrosion aux bains. Des inhibiteurs de corrosion communément utilisés à cet effet sont les chlorures d'alkylpyridinium, l'hexaméthylènetétramine et les composés organiques comprenant des groupements sulfonium. On a toutefois observé, en pratique, que malgré la présence d'inhibiteurs de corrosion dans les bains acides, ceux-ci provoquent malgré tout une corrosion rapide des masses métalliques traitées. Cette corrosion serait imputable à la présence d'oxydants dans le bain principalement des ions ferriques. Pour remédier à cet inconvénient, on a déjà préconisé d'ajouter des réducteurs au bain, par exemple du chlorure stanneux, en plus des inhibiteurs de corrosion. L'utilisation de réducteurs dans le bain est généralement onéreuse, surtout dans le cas de bains non désaérés car on enregistre alors une perte appréciable en réducteurs, due à leur consommation intempestive par l'oxygène du bain, cette consommation étant d'autant plus importante que la température est plus élevée. Il s'ensuit par ailleurs une augmentation de la contamination du bain par les réducteurs dont certains, en particulier les ions stanneux, sont généralement jugés dangereux pour l'écologie, notamment lorsque les bains résiduaires sont évacués dans des lacs ou des cours d'eaux.It is common practice to incorporate corrosion inhibitors in baths. Corrosion inhibitors commonly used for this purpose are alkylpyridinium chlorides, hexamethylenetetramine and organic compounds comprising sulfonium groups. However, it has been observed, in practice, that despite the presence of corrosion inhibitors in the acid baths, these nonetheless cause rapid corrosion of the treated metallic masses. This corrosion would be due to the presence of oxidants in the bath mainly ferric ions. To overcome this drawback, it has already been recommended to add reducing agents to the bath, for example stannous chloride, in addition to corrosion inhibitors. The use of reducers in the bath is generally expensive, especially in the case of non-deaerated baths because there is then an appreciable loss in reducers, due to their untimely consumption by the oxygen of the bath, this consumption being all the more important. that the temperature is higher. It also results in an increase in the contamination of the bath by reducing agents, some of which, in particular stannous ions, are generally considered dangerous for the ecology, in particular when the residual baths are discharged into lakes or watercourses. .

L'invention vise à remédier aux inconvénients précités, en fournissant un procédé pour inhiber la corrosion de masses métalliques au contact de bains acides contenant des ions ferriques, qui soit fiable, économique et inoffensif pour l'environnement.The invention aims to remedy the aforementioned drawbacks by providing a method for inhibiting corrosion of metallic masses in contact with acid baths containing ferric ions, which is reliable, economical and harmless for the environment.

L'invention concerne dès lors un procédé pour inhiber la corrosion d'une masse métallique au contact d'un bain acide contenant des ions ferriques; selon l'invention, on fait circuler une partie au moins du bain à travers un empilage de feutres en carbone non graphitique ou en graphite, alternant avec des corps solides en fer ou en alliage de fer.The invention therefore relates to a method for inhibiting corrosion of a metallic mass in contact with an acid bath containing ferric ions; according to the invention, at least part of the bath is circulated through a stack of non-graphitic carbon or graphite felts, alternating with solid bodies of iron or an iron alloy.

Le procédé selon l'invention s'applipue à tout bain acide contenant des ions ferriques, capable de provoquer une oxydation électrochimique de la masse métallique dans les conditions d'utilisation du bain. Les ions ferriques présents dans le bain peuvent provenir de sources très diverses telles que, par exemple, de couches oxydées à la surface de la masse métallique, d'une corrosion du circuit de manutention du bain, d'une incrustation à la surface de la masse métallique, d'impuretés présentes dans le bain acide; dans le cas de bains acides aqueux, des ions ferriques peuvent parfois être apportés par l'eau utilisée pour la préparation du bain.The method according to the invention applies to any acid bath containing ferric ions, capable of causing an electrochemical oxidation of the metal mass under the conditions of use of the bath. The ferric ions present in the bath can come from very diverse sources such as, for example, from oxidized layers on the surface of the metallic mass, from corrosion of the bath handling circuit, from incrustation on the surface of the metallic mass, of impurities present in the acid bath; in the case of aqueous acid baths, ferric ions can sometimes be provided by the water used for the preparation of the bath.

Dans le procédé selon l'invention, il convient évidemment d'éviter que la masse métallique traitée dans le bain soit couplée à l'empilage.In the process according to the invention, it is obviously advisable to avoid that the metallic mass treated in the bath is coupled to the stack.

On peut faire usage de divers modes de traitement du bain dans l'empilage. Selon un premier mode de traitement, on prélève périodiquement une fraction du bain et on la fait circuler à travers l'empilage pendant un temps prédéterminé suffisant pour réduire une partie au moins des ions ferriques qu'elle contient; la fraction est ensuite renvoyée dans le bain. Selon un second mode de traitement, qui est préféré, on fait circuler la totalité du bain à travers l'empdage, selon un débit réglé pour qu'à la sortie de l'empilage, sa teneur en ions ferriques soit tombée au-dessous d'une valeur prédéterminée. Dans ce mode de traitement préféré, le bain peut être mis à circuler à travers l'empilage périodiquement ou de manière continue.Various methods of bath treatment can be used in the stack. According to a first treatment mode, a fraction of the bath is periodically removed and it is circulated through the stack for a predetermined time sufficient to reduce at least part of the ferric ions which it contains; the fraction is then returned to the bath. According to a second treatment method, which is preferred, the entire bath is circulated through the packing, at a rate adjusted so that at the exit of the stack, its ferric ion content has fallen below d 'a predetermined value. In this preferred mode of treatment, the bath can be circulated through the stack periodically or continuously.

On régie généralement le traitement du bain dans l'empilage, de manière que la quantité résiduelle d'ions ferriques dans le bain en contact avec la masse métallique n'excède pas 300 mg/1, de préférence 200 mg/1. Des teneurs résiduelles n'excédant pas 150 mg/I sont conseillées, notamment celles comprises entre 1 et 100 mg/I.The treatment of the bath in the stack is generally governed, so that the residual quantity of ferric ions in the bath in contact with the metallic mass does not exceed 300 mg / 1, preferably 200 mg / 1. Residual contents not exceeding 150 mg / I are recommended, especially those between 1 and 100 mg / I.

Dans une forme d'exécution avantageuse du procédé selon l'invention, on met en oeuvre un empilage dans lequel les feutres sont formés de fibres dont le diamètre n'excède pas 25 microns, de préférence 15 microns. On préfère mettre en oeuvre des empilages de corps en acier doux et de feutres en carbone non graphitique, dont le diamètre des fibres est compris entre 8 et 12 microns.In an advantageous embodiment of the method according to the invention, a stack is used in which the felts are formed of fibers whose diameter does not exceed 25 microns, preferably 15 microns. It is preferred to use stacks of mild steel bodies and non-graphitic carbon felts, the fiber diameter of which is between 8 and 12 microns.

Les corps solides de l'empilage peuvent avoir tous profils permettant une grande surface de contact avec les feutres. Dans une forme de réalisation particulière de l'invention, on utilise un empilage dans lequel les corps solides en fer ou en alliage du fer sont des plaques qui alternent avec les feutres en carbone ou en graphite.The solid bodies of the stack can have any profile allowing a large contact surface with the felts. In a particular embodiment of the invention, a stack is used in which the solid bodies of iron or of iron alloy are plates which alternate with carbon or graphite felts.

Dans une forme d'exécution préférée du procédé selon l'invention, on met en oeuvre un empilage dans lequel les corps solides sont des plaques perforées et on fait circuler le bain à travers l'empilage, dans une direction transversale aux plaques et aux feutres. Dans le cas de grandes installations mettant en oeuvre des volumes de bain importants, il peut être avantageux de faire usage de plusieurs empilages disposés en dérivation sur le sens de circulation du bain.In a preferred embodiment of the method according to the invention, a stack is used in which the solid bodies are perforated plates and the bath is circulated through the stack, in a direction transverse to the plates and the felts. In the case of large installations using large volumes of bath, it may be advantageous to make use of several stacks arranged in bypass on the direction of circulation of the bath.

Le procédé selon l'invention s'applique également aux bains acides contenant un inhibiteur de corrosion. Celui-ci peut-être, par exemple, du chlorure d'alkylpyridinium qui est avantageusement sélectionné parmi ceux dérivés d'alkanes possédant de 10 à 18 atomes de carbone. Dans le cas de bains d'acide chlorhydrique, on peut par exemple mettre en oeuvre du chlorure de cétyl-, de myristil- ou de laurylpyridinium, en quantité réglée entre 0,5 et 5000 mg par kg du bain, de préférence entre 2 et 500 mg/kg. D'autres exemples d'inhibiteurs de corrosion utilisables dans les bains traités par le procédé selon l'invention sont l'hexaméthylènetétramine et le formol.The method according to the invention also applies to acid baths containing a corrosion inhibitor. This may be, for example, alkylpyridinium chloride which is advantageously selected from those derived from alkanes having from 10 to 18 carbon atoms. In the case of hydrochloric acid baths, it is possible, for example, to use cetyl-, myristil- or laurylpyridinium chloride, in an amount regulated between 0.5 and 5000 mg per kg of the bath, preferably between 2 and 500 mg / kg. Other examples of corrosion inhibitors which can be used in the baths treated by the process according to the invention are hexamethylenetetramine and formalin.

Le procédé selon l'invention s'applique à toute masse métallique traitée dans un bain acide contenant des ions ferriques susceptible d'attaquer la masse métallique. Il s'applique notamment aux masses métalliques comprenant du fer, du chrome, du zinc, du cobalt, du nickel ou un alliage contenant au moins un de ces métaux. Il trouve une application spécialement intéressante dans le cas de masses métalliques traitées avec des bains aqueux d'acide minéral contenant des ions ferriques. Il est notamment applicable à la désincrustation, au moyen de tels bains, d'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. D'autres exemples d'application sont la desincrustation de la zone de réfrigération des colonnes en acier ou en fonte servant à la cristallisation de bicarbonate de sodium dans le procédé de fabrication de la soude à l'ammoniaque, l'élimination d'incrustations de carbonate de calcium des chaudières en acier, la manutention d'acides minéraux en solution aqueuse dans des canalisations ou des réservoirs en acier ou en fonte, le décapage de produits métallurgiques tels que des toles, des barres, des poutrelles ou des rails en acier ordinaire, et tout spécialement le décapage des produits du laminage à froid destinés à un traitement de galvanisation, tels que feuillards et fils tréfilés. Dans ces diverses applications, le bain acide peut par exemple être une solution aqueuse d'acide sulfurique ou d'acide chlorhydrique. Les solutions aqueuses contenant de 0,01 à 6 moles d'acide chlorhydrique par litre conviennent généralement bien.The method according to the invention applies to any metallic mass treated in an acid bath containing ferric ions capable of attacking the metallic mass. It applies in particular to metallic masses comprising iron, chromium, zinc, cobalt, nickel or an alloy containing at least one of these metals. It finds a particularly interesting application in the case of metallic masses treated with aqueous baths of mineral acid containing ferric ions. It is particularly applicable to descaling, by means of such baths, of nickel or nickel alloy evaporators used to crystallize sodium chloride from caustic brines produced by electrolysis of sodium chloride brine in a cell. permeable diaphragm electrolysis. Other examples of application are the descaling of the refrigeration zone of the steel or cast iron columns used for the crystallization of sodium bicarbonate in the process for manufacturing soda with ammonia, the elimination of incrustations of calcium carbonate from steel boilers, handling of mineral acids in aqueous solution in steel or cast iron pipes or tanks, pickling of metallurgical products such as sheets, bars, beams or rails of ordinary steel , and especially the pickling of cold rolling products intended for a galvanizing treatment, such as strips and drawn wires. In these various applications, the acid bath can for example be an aqueous solution of sulfuric acid or hydrochloric acid. Aqueous solutions containing from 0.01 to 6 moles of hydrochloric acid per liter are generally suitable.

L'intérêt de l'invention va apparaître au cours de la description suivante de quelques exemples d'application, en référence aux dessins annexés.

  • La figure 1 est un schéma d'une installation mettant en oeuvre une forme de réalisation particulière du procédé selon l'invention;
  • La figure 2 montre un détail de l'installation de la figure 1, à plus grande échelle et en section transversale verticale;
  • Les figures 3 à 5, sont des diagrammes reproduisant des résultats d'essais.
The advantage of the invention will appear during the following description of some application examples, with reference to the accompanying drawings.
  • FIG. 1 is a diagram of an installation implementing a particular embodiment of the method according to the invention;
  • Figure 2 shows a detail of the installation of Figure 1, on a larger scale and in vertical cross section;
  • Figures 3 to 5 are diagrams reproducing test results.

Dans ces figures, des mêmes notations de référence désignent des éléments identiques.In these figures, the same reference notations designate identical elements.

L'installation schématisée à la figure 1 comprend une cuve de décapage 1, contenant une masse en acier ordinaire ou en fonte 2 à décaper. Celle-ci consiste par exemple en un empilage de bobines de fils tréfilés ou de feuillards. Le décapage est assuré au moyen d'un bain 3 constitué d'une solution normale d'acide chlorhydrique.The installation shown diagrammatically in FIG. 1 comprises a pickling tank 1, containing a mass of ordinary steel or cast iron 2 to be pickled. This consists, for example, of a stack of coils of drawn wires or of strips. The pickling is carried out by means of a bath 3 consisting of a normal hydrochloric acid solution.

La cuve de décapage est reliée, par l'intermédiaire d'une pompe 4 et de canalisations 5 et 6, à une cellule de traitement 7. Celle-ci est formée (fig. 2) d'une chambre tubulaire verticale 8 contenant un empilage de disques perforés horizontaux en acier 9, alternant avec des feutres horizontaux 10 en fibres de carbone non graphitique. Les disques 9 sont traversés de perforations verticales tubulaires 11.The pickling tank is connected, by means of a pump 4 and pipes 5 and 6, to a treatment cell 7. This is formed (fig. 2) of a vertical tubular chamber 8 containing a stack of perforated horizontal steel discs 9, alternating with horizontal felt 10 made of non-graphitic carbon fibers. The discs 9 are crossed by tubular vertical perforations 11.

Pendant le décapage de la masse métallique 2 dans le bain 3 des ions ferriques sont libérés de manière continue dans le bain 3. Selon l'invention, on fait circuler le bain 3 de la cuve 1 dans la cellule 7, via les canalisations 5 et 6 et la pompe 4. La mise en circulation du bain 3 dans la cellule 7 peut être opérée de manière périodique ou de manière continue. Dans la cellule 7, le bain circule dans les perforations 11 au contact des disques 9 et à travers les feutres 10, et les ions ferriques sont réduits en ions ferreux. En réglant convenablement le débit du bain 3 dans la cellule 7, il est possible de compenser la quantité d'ions ferriques qui sont libérés dans le bain 3, dans la cuve 1, par une réduction d'une quantité équivalente d'ions ferriques dans la cellule 7.During the pickling of the metallic mass 2 in the bath 3 ferric ions are continuously released in the bath 3. According to the invention, the bath 3 is circulated from the tank 1 to the cell 7, via the pipes 5 and 6 and the pump 4. The circulation of the bath 3 in the cell 7 can be carried out periodically or continuously. In cell 7, the bath circulates in the perforations 11 in contact with the discs 9 and through the felts 10, and the ferric ions are reduced to ferrous ions. By properly adjusting the flow rate of the bath 3 in the cell 7, it is possible to compensate for the quantity of ferric ions which are released in the bath 3, in the tank 1, by a reduction of an equivalent quantity of ferric ions in cell 7.

Les exemples d'application qui vont suivre vont mettre en évidence l'intérêt du procédé selon l'invention. Dans ces exemples, on a mis en oeuvre un volume de 10 1 d'une solution aqueuse quatre fois normale d'acide chlorhydrique contenant 10 g d'ions ferriques par litre, et on l'a fait transiter en permanence à travers un empilage de disques métalliques perforés, l'aire de la section transversale de chaque disque étant de 20 cm2. On a mesuré la variation, en fonction du temps, de la concentration en ions ferriques du bain. On a fait usage à cet effet, d'une cellule de mesure électrochimique comprenant une électrode tournante en platine et une contre- électrode fixe en platine, immergées dans le bain d'acide chlorhydrique, et une électrode de référence au calomel, saturée en KCI; au moyen d'un circuit potentiostatique, on a maintenu l'electrode tournante à un potentiel constant de - 150 mV par rapport à l'électrode de référence et on a mesuré l'intensité du courant électrique dans la cellule de mesure, qui est sensiblement proportionnelle à la concentration des ions ferriques.The application examples which follow will demonstrate the advantage of the process according to the invention. In these examples, a volume of 10 l of a four-fold aqueous hydrochloric acid solution containing 10 g of ferric ions per liter was used, and it was continuously passed through a stack of perforated metal discs, the cross-sectional area of each disc being 20 cm 2 . The variation, as a function of time, of the concentration of ferric ions in the bath was measured. For this purpose, use was made of an electrochemical measuring cell comprising a rotating platinum electrode and a fixed platinum counter electrode, immersed in the hydrochloric acid bath, and a calomel reference electrode, saturated with KCI ; by means of a potentiostatic circuit, the rotating electrode was maintained at a constant potential of - 150 mV relative to the reference electrode and the intensity of the electric current in the measuring cell was measured, which is substantially proportional to the concentration of ferric ions.

Aux diagrammes des figures 3 à 5, l'échelle des abscisses mentionne le temps, en minutes, et l'échelle des ordonnées indique la concentration du bain en ions ferriques, exprimée en g/I.In the diagrams of FIGS. 3 to 5, the abscissa scale indicates the time, in minutes, and the ordinate scale indicates the concentration of the bath in ferric ions, expressed in g / I.

Exemple 1 (exemple deExample 1 (example of référence)reference)

L'empilage a consisté en treize disques de fonte alternant avec des anneaux en polychlorure de vinyle.The stack consisted of thirteen cast iron discs alternating with polyvinyl chloride rings.

Le débit de la solution à travers l'empilage a été de 150 1/h. Les résultats de l'essai sont reproduits sur la courbe (12) du diagramme de la figure 3.The flow rate of the solution through the stack was 150 l / h. The results of the test are reproduced on the curve (12) of the diagram in FIG. 3.

Exemples 2 (conforme àExamples 2 (according to l'invention)the invention)

On a répété l'ensemble des conditions opératoires de l'essai de l'exemple 1, dans lequel on a remplacé l'empilage des disques de fonte par un empilage de treize disques perforés en fonte alternant avec douze feutres en graphite. Les résultats de l'essai sont matérialisés par la courbe (13) du diagramme de la figure 3. On observe qu'à l'issue de 55 minutes d'essai, la concentration du bain en ions ferriques tombe sous 1 % de sa valeur initiale.All the operating conditions of the test of Example 1 were repeated, in which the stacking of the cast iron discs was replaced by a stack of thirteen perforated cast iron discs alternating with twelve graphite felts. The results of the test are shown by the curve (13) in the diagram in FIG. 3. It is observed that after 55 minutes of testing, the concentration of the ferric ion bath drops below 1% of its value. initial.

Exemple 3, 4 et 5 (conformes àExample 3, 4 and 5 (according to l'invention)the invention)

Dans chacun de ces exemples, on a mis en oeuvre un empilage de disques en acier perforés (d'aire égale à 20 cm2) alternant avec des feutres en graphite. Le nombre de feutres en graphite a été respectivement de 6 dans l'exemple 3 et de 12 dans l'exemple 4. Dans l'exemple 5, on a fait usage de deux empilages de 13 disques (et 12 feutres), les deux empilages étant montés en dérivation sur le circuit de la solution d'acide chlorhydrique. Le débit de la solution a été de 200 1/h dans chaque essai.In each of these examples, a stack of perforated steel discs (of area equal to 20 cm 2) was used alternating with graphite felts. The number of graphite felts was 6 in Example 3 and 12 in Example 4, respectively. In Example 5, two stacks of 13 discs (and 12 felts) were used, the two stacks being mounted in bypass on the hydrochloric acid solution circuit. The flow rate of the solution was 200 l / h in each test.

Les résultats des essais sont reproduits au diagramme de la figure 4, où les courbes (14), (15) et (16) concernent respectivement les essais des exemples 3,4 et 5. On y observe que le nombre de disques mis en oeuvre dans la cellule électrochimique a une incidence directe sur l'inhibition de la corrosion; dans le cas de l'exemple 5, la concentration résiduelle en ions ferriques tombe déjà sous 1 % de sa valeur initiale, à l'issue de 17 minutes de traitement.The results of the tests are reproduced in the diagram of FIG. 4, where the curves (14), (15) and (16) relate respectively to the tests of Examples 3, 4 and 5. It is observed there that the number of disks used in the electrochemical cell has a direct impact on the inhibition of corrosion; in the case of Example 5, the residual concentration of ferric ions already falls below 1% of its initial value, after 17 minutes of treatment.

Exemples 6, 7 et 8 (conformes à l'invention)Examples 6, 7 and 8 (in accordance with the invention)

Dans chacun de ces exemples, on a mis en oeuvre un empilage de 13 disques en acier (et 12 feutres en carbone non graphitique), et on a fait varier le débit de la solution dans les empilages: 150 1/h dans l'exemple 6, 200 1/h dans l'exemple 7 et 500 1/h dans l'exemple 8. Les résultats des essais sont reproduits au diagramme de la figure 5, où les courbes (17), (18) et (19) concernent respectivement les exemples 6, 7 et 8. On y observe que, toutes autres choses restant égales, avec un débit de 500 1/h, la concentration résiduelle en ions ferriques du bain tombe sous 1 % de sa valeur de départ, déjà après 11 minutes de traitement.In each of these examples, a stack of 13 steel discs (and 12 non-graphitic carbon felt) was used, and the flow rate of the solution in the stacks was varied: 150 l / h in the example 6, 200 1 / h in example 7 and 500 1 / h in example 8. The results of the tests are reproduced in the diagram of FIG. 5, where the curves (17), (18) and (19) relate Examples 6, 7 and 8 respectively. It is observed there that, all other things remaining equal, with a flow rate of 500 l / h, the residual concentration of ferric ions in the bath falls below 1% of its initial value, already after 11 minutes of treatment.

Exemple 9 (conforme àExample 9 (according to l'invention)the invention)

On a répété les conditions de l'exemple 8, en utilisant deux empilages identiques (13 disques en acier et douze feutres en carbone) disposés en parallèle dans le circuit de la solution. Les résultats de l'essai sont reproduits par la courbe (20) du diagramme de la figure 5. On y observe que 8 minutes suffisent pour amener la teneur en ions ferriques du bain, de 10 g/1 à 0,1 g/1.The conditions of Example 8 were repeated, using two identical stacks (13 steel discs and twelve carbon felts) arranged in parallel in the solution circuit. The results of the test are reproduced by the curve (20) of the diagram of FIG. 5. It is observed there that 8 minutes are sufficient to bring the content of ferric ions in the bath, from 10 g / 1 to 0.1 g / 1 .

Une comparaison des résultats des exemples 2 à 9 (conformes à l'invention) avec ceux de l'exemple 1 (essai de référence) fait apparaître immédiatement que le procédé selon l'invention permet de réaliser une inhibition rapide et efficace de la corrosion, celle-ci étant proportionnelle à la concentration résiduelle en ions ferriques du bain.A comparison of the results of Examples 2 to 9 (in accordance with the invention) with those of Example 1 (reference test) immediately shows that the process according to the invention makes it possible to achieve rapid and effective corrosion inhibition, this being proportional to the residual concentration of ferric ions in the bath.

Claims (9)

1. Process for inhibiting the corrosion of a mass of metal (2) in contact with an acid bath (3) containing ferric ions, characterized in that at least a part of the bath (3) is circulated through a stack (7) of felts (10) made of nongraphitic carbon or of graphite, alternating with solid bodies (9) made of iron or of an iron alloy.
2. Process according to Claim 1, characterized in that the solid bodies (9) are plates.
3. Process according to Claim 2, characterized in that use is made, in the stack, of plates (9) which are perforated and the bath (3) is circulated through the stack (7), transversely to the plates (9) and to the felts (10).
4. Process according to any one of Claims 1 to 3, characterized in that use is made of felts (10) the fibre diameter of which is at most equal to 25 microns.
5. Process according to any one of Claims 1 to 4, characterized in that use is made of a stack (7) in which the bodies (9) are made of mild steel and the felts (10) are made of nongraphitic carbon.
6. Process according to any one of Claims 1 to 5, characterized in that the bath (3) employed is an aqueous bath of hydrochloric acid.
7. Process according to any one of Claims 1 to 6, characterized in that the circulation of the bath (3) through the stack (7) is set so as to maintain a ferric ion content at most equal to 150 mg/I in the bath which is in contact with the mass of metal (2).
8. Process according to any one of Claims 1 to 7, characterized in that the mass of metal (2) contains chromium, zinc, iron, cobalt, nickel, or an alloy containing at least one of these metals.
9. Process according to Claim 8, characterized in that the mass of metal (2) is a metallurgical product made of steel or cast iron.
EP85200527A 1984-04-16 1985-04-04 Process for inhibiting corrosion of a metallic mass in contact with an acidic bath containing ferric ions Expired EP0162491B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT85200527T ATE31083T1 (en) 1984-04-16 1985-04-04 METHOD OF INHIBITING CORROSION OF METAL MASS IN CONTACT WITH AN ACID BATH CONTAINING IRON III IONS.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8406098 1984-04-16
FR8406098A FR2562914A1 (en) 1984-04-16 1984-04-16 PROCESS FOR INHIBITING CORROSION OF A METAL MASS IN CONTACT WITH AN ACIDIC BATH CONTAINING AN OXIDANT

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EP0162491A1 EP0162491A1 (en) 1985-11-27
EP0162491B1 true EP0162491B1 (en) 1987-11-25

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EP (1) EP0162491B1 (en)
JP (1) JPS60234983A (en)
AT (1) ATE31083T1 (en)
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FR (1) FR2562914A1 (en)

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JPS6432197A (en) * 1987-07-29 1989-02-02 Hitachi Ltd Plant for retreatment of nuclear fuel
NL8900106A (en) * 1989-01-18 1990-08-16 Avf Chemische Ind En Handelson METHOD FOR CLEANING METALS, FOR example IRONS OR STEELS, INTERNAL SURFACES OF INDUSTRIAL EQUIPMENT.
US6329206B1 (en) * 1999-06-22 2001-12-11 Henkel Corporation Method of determining inhibitor concentrations in inhibited acidic pickling solutions
US9896738B2 (en) 2015-05-28 2018-02-20 Savannah River Nuclear Solutions, Llc Process for dissolving aluminum for recovering nuclear fuel

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NL6406533A (en) * 1964-06-09 1965-12-10
JPS502372A (en) * 1973-05-15 1975-01-10
DE2457235A1 (en) * 1974-12-04 1976-06-10 Peter Vodicka Protecting descaled pickled or cleaned metal articles - against attack by ferric cations by redn. using metals or water soluble cpds.
JPS5215496A (en) * 1975-07-28 1977-02-05 Mitsubishi Electric Corp Method for production of ferrous nitrate

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US4765958A (en) 1988-08-23
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DE3561072D1 (en) 1988-01-07
ES542242A0 (en) 1985-12-16
JPH0465908B2 (en) 1992-10-21
ATE31083T1 (en) 1987-12-15
EP0162491A1 (en) 1985-11-27
ES8603596A1 (en) 1985-12-16

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