WO1993019365A1 - Method of analysis of a metallic sample by dissolving the surface thereof and device for carrying out said method - Google Patents

Method of analysis of a metallic sample by dissolving the surface thereof and device for carrying out said method Download PDF

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Publication number
WO1993019365A1
WO1993019365A1 PCT/FR1993/000277 FR9300277W WO9319365A1 WO 1993019365 A1 WO1993019365 A1 WO 1993019365A1 FR 9300277 W FR9300277 W FR 9300277W WO 9319365 A1 WO9319365 A1 WO 9319365A1
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WO
WIPO (PCT)
Prior art keywords
sample
electrolyte
cell
dissolution
reference electrode
Prior art date
Application number
PCT/FR1993/000277
Other languages
French (fr)
Inventor
Kévin OGLE
Paul Lodi
Alain Storhaye
Original Assignee
Techmetal Promotion
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Publication date
Application filed by Techmetal Promotion filed Critical Techmetal Promotion
Publication of WO1993019365A1 publication Critical patent/WO1993019365A1/en

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/416—Systems
    • G01N27/42—Measuring deposition or liberation of materials from an electrolyte; Coulometry, i.e. measuring coulomb-equivalent of material in an electrolyte
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/20—Metals
    • G01N33/208—Coatings, e.g. platings

Definitions

  • the invention relates to the field of analysis of metallic materials, more particularly their analysis by progressive dissolving of their surface.
  • the new electrolyte enters the cell and leaves it charged with products from the dissolution of the free surface of the sample. It is then sent to the spectrometer. This determines the intensities of the radiation emitted by the electrolyte in the plasma for the wavelengths characteristic of the elements which it is desired to detect, these intensities being directly proportional to the concentrations of these elements in the solution.
  • the evolution of these intensities over time, as the dissolution of the surface continues, reflects the gradient of concentration of the various elements in the coating from the initial surface to the metal substrate, or even in the substrate itself if the dissolution is continued even further. We can, in particular, seek to determine the nature of the successive phases according to the thickness of the coating.
  • the object of the invention is to propose a method of surface analysis of metal samples, always based on the coupling of an electrochemical dissolution cell and a spectrometer, but free from the drawbacks mentioned above, that is to say faithfully accounting for the gradients of concentration of the various elements of the coating, and not requiring long preliminary tests before the final analysis.
  • the invention relates to a method of analysis of a metallic sample according to which a dissolution of the surface of said sample is carried out by means of an electrolyte flowing on said surface, and determines continuously, after the passage of the electrolyte over the sample, the content of the electrolyte in the various constituents of said surface which it has dissolved, characterized in that the potential of said sample is continuously determined relative to a reference electrode immersed in the electrolyte, and a given electrical parameter is imposed on said sample, so as to cause the successive dissolution of the different phases present on the surface of the sample.
  • This electrical parameter can be the potential of the sample or the intensity of the current flowing through it.
  • the invention also relates to a device for analyzing a metal sample of the type comprising a reservoir containing an electrolyte, a dissolution cell, one wall of which includes a surface of said sample, means for passing said cell through. electrolyte, and means for continuously analyzing said electrolyte after crossing the ladi- you cell, characterized in that it comprises means for mesu ⁇ rer continuously the potential difference between said sample and a reference electrode immersed in the electrolyte inte ⁇ laughing of said cell, and means for imposing to said sample a potential determined with respect to said reference electrode, or a determined intensity. for the current flowing through it.
  • the device also comprises an ion exchange membrane, separating the cell into two compartments.
  • the invention consists in carrying out in a successive and controlled manner the dissolution of the different phases which the metal sample comprises as and when they appear during its dissolution, and in determining the composition of these phases according to that of the electrolyte which dissolved them.
  • FIG. 1 represents an electrochemical cell according to the invention with its appendices, front view in section along II- II;
  • FIGS. 1, 2 and 3 show the evolution over time on the one hand of the potential difference between a sample and a reference electrode, and on the other hand of the intensities emitted simultaneously by the various elements in a spectrometer during a analysis performed by simple progressive dissolution of the sample by the electrolyte in the cell according to the invention;
  • - Figure 5 shows the evolution of the same parameters during an analysis by imposing successive constant dissolu ⁇ tion potentials on the sample placed in the cell according to the invention.
  • FIGS. 1, 2 and 3 An example of a device according to the invention is shown in FIGS. 1, 2 and 3.
  • the cell comprises a body 1 which is substantially parallelepiped in which a cylindrical cavity 2 is formed, open on the upper face of the body 1.
  • the body 1 is also traversed by a channel 3 opening on the one hand on a lateral face 4 of the body 1, and on the other hand in the cylindrical cavity 2.
  • a porous membrane 5 which is preferably an exchanging membrane ion gayer, for example anion exchange. This has an area at least sufficient to completely seal the orifice 6 of the channel 3 opening onto the lateral face 4 of the body 1.
  • the membrane 5 is pressed against the lateral face 4 by means of a piece 7 detachably fixed to the body 1.
  • This part 7 is pierced right through by an orifice 8 which extends the orifice 6 of the channel 3 of the body 1. It also includes a channel 9 for supplying the electrolyte inside the orifice 8.
  • This channel 9 opens out to the outside of the cell and is provided with means (not shown in FIG. 1) for its connection to a condui ⁇ te 23 connected to an electrolyte reservoir 24.
  • Preferably channel 9 opens into the lower part of the orifice 8 of the part 7.
  • This likewise comprises a channel 10 for discharging the electrolyte opening out on the one hand into the upper part of the orifice 8 of the part 7, and on the other hand outside the cell. It is connected to a pipe 27 connected to a spectrometer 25 which continuously analyzes the electrolyte charged with the materials which it has dissolved in its passage over the sample 14. This arrangement of the inlet and the outlet of the electrolyte in the cell allows rapid evacuation of the gases formed during the operation.
  • the part 7 finally comprises a housing 11 into which a reference electrode 12 can be inserted, the end 13 of which opens out in the orifice 8.
  • the sheet metal sample 14 On the external face of the part 7 is pressed the sheet metal sample 14, so as to close the orifice 8, with the face to be analyzed turned towards the inside of the cell. .
  • the orifices of the channels 9 and 10 opening into the orifice 8 of the part 7 are shaped so as to direct the flows of the electrolyte towards the surface of the sample 14.
  • An electrical contact 15 is connected to the external face of the sample 14. All these parts are held together and can be separated from one another to be changed.
  • the installation also includes an electrode 18, preferably made of platinum, immersed in the cylindrical cavity 2.
  • the platinum electrode 18, the electrical contact 15 and the reference electrode 12 are connected to a poten ⁇ tiostat 19, respectively by connections 20, 21, 22.
  • the potentiostat 19 makes it possible to maintain a constant and known potential difference between the platinum electrode 18, placed as a cathode, and the sample 14 to be analyzed, placed at the anode, and to measure the potential difference between the sample 14 and the reference electrode 12.
  • the electrolyte is set in motion by a pump 25 inserted between the cell 1 and the spectrometer 25 .
  • the anodic compartment defined by the sample 14 and the anion exchange membrane 5 may have a volume of approximately 0.15 ml or even less, and the surface of the sample 14 exposed to the electrolyte is of the order of 0.5 cm 2 .
  • the electrolyte circulates in the installation with a flow rate of the order of 2 ml / min.
  • the cathode compartment has a volume of approximately 10 ml.
  • the platinum electrolyte has an area of 10 cm 2 .
  • the reference electrode is a silver wire 0.5 mm in diameter coated by electrodeposition with a layer of silver chloride.
  • the role of the anion exchange membrane 5 is threefold. On the one hand, it makes it easy to produce a low-volume anode compartment, which goes hand in hand with a reduced residence time for the electrolyte. The reaction time of the apparatus is thus reduced, its resolving power is increased in its capacity to discriminate the different phases of the sample to be analyzed, and the homogeneity of the composition of the electrolyte is improved in the anode compartment.
  • the membrane 5 makes it possible to isolate the anode and cathode compartments while allowing the electric current to pass, and the chemical reactions which can occur in the cathode compartment (in the following example, a release hydrogen and a deposit of metal ions) do not interfere with the measurements.
  • the sample is a sample of galvanized steel sheet of the "Extragai ®" type, conventionally prepared in a zinc bath containing 0.16% aluminum and 0.04% lead.
  • the spectrometer is an inductively coupled plasma optical emission spectrometer, detecting the following wavelengths for the various elements to be analyzed: for zinc 3302.6 ⁇ , for iron 2599.4 ⁇ , for aluminum 3961.5 ⁇ . This type of spectrometer is preferably chosen for the speed of its response.
  • the electrolyte is a 1.2 M hydrochloric acid solution. Initially, the cell according to the invention can be used as if it were a conventional dissolution cell, that is to say by not connecting the cathode 18 to the potentiostat 19.
  • FIG. 4 shows the changes over time, firstly of the potential difference E measured between the reference electrode 12 and the sample 14, translated by the curve 28, and secondly of the intensities emission of the spectrometer 25 corresponding to the various elements sought: zinc corresponds to the curve 29, iron to the curve 30 and aluminum to the curve 31.
  • the height of each peak of said curves is well proportional to • the concentration in the electrolyte of the element it represents, but the relative heights of the different peaks are not representative of the respective proportions of the different elements in the coating of the sample 14.
  • the curve 28 indicates the presence of two phases in the coating, the respective dissolutions of which impose on the sample 14 potentials of the order d e - approximately 940 mV for the first phase, and from - 800 to - 650 mV for the second phase.
  • the curves 29, 30 and 31 indicate further that the 'pre ⁇ Mière phase is composed of zinc and a certain amount of alu ⁇ minium likely to be very low, and that the second phase is an alloy of iron and 'aluminum. After dissolution of this second phase, the potential difference E becomes stable and no reaction is observed which could correspond to a dissolution of the steel substrate. Such a reaction, under the conditions of the experiment, could only occur in the presence of a catalyst. Finally, note that the spread over time of the different peaks of emission intensity I is not strictly proportional tional to the thickness of the different phases: it is also a function of their dissolution rate which may be different for each of them.
  • FIG. 5 shows the changes over time of the same parameters as the previous figure: the curve 28 represents the potential difference E between the reference electrode 12 and the sample 14, the curves 29, 30 and 31 represent the emission intensities I of zinc, iron and aluminum in the spectrometer.
  • the experiment proceeds as follows: the electrical circuit is first left open for 50 s, and a potential of - 1044 mV at the anode (sample 14) is established. Then we impose on the anode a potential of - 944 mV. We then observe the dissolution of a first phase essentially comprising zinc with a very small amount of aluminum. This is obviously the dissolution of the outer layer of the coating, where no iron is observed.
  • the apparatus according to the invention makes it possible to carry out an analysis of the phases of the coating substantially finer than by the conventional method of dissolution without checking the potential of the sample, even when this method is improved. by measuring the potential of the sample.
  • the invention makes it possible to easily interrupt the experiment after the dissolution of a given phase, so as to allow microscopic analysis of the interfa ⁇ cial alloys.
  • the accuracy of this analysis method is much less dependent on the choice of electrolyte than is the conventional dissolution method with no imposed potential.
  • the potentiostat 19 can be replaced by an intensiostat, so as to impose a given intensity on the current flowing through the sample.
  • the evolution of the composition of the electrolyte can be followed as the sample dissolves, while relating it to the potentials taken successively by the sample and measured by relative to the reference electrode.
  • controlling the dissolution potential or the intensity of the current makes it possible to control the selectivity of the dissolution and its kinetics.
  • the invention is in no way limited to the example which has just been described.
  • other cell morphologies are imaginable, so as to analyze samples of various shapes, and the inductively coupled plasma emission spectrometer can be replaced by any other type of device capable of continuously analyzing the electrolyte.
  • the invention is applicable to any metallurgical sample for which it is desired to know the surface composition, whether or not it has a metallic coating separate from the base metal.

Abstract

Device for analysing a metallic sample (14) comprising a reservoir (24) containing an electrolyte, a dissolution cell (1) having one wall formed by the surface of said sample (14), means (9, 10, 23, 26, 27) for passing said electrolyte through said cell (1), means (25) for continuously analysing said electrolyte after its passage through said cell (1), means for continuously measuring the potential difference between said sample (14) and a reference electrode (12) immersed in the electrolyte in said cell (1), and means for giving said sample either a potential determined with expect to said reference electrode or a constant current moment.

Description

METHODE D'ANALYSE D'UN ECHANTILLON METALLIQUE PAR DISSOLUTION METHOD OF ANALYSIS OF A METAL SAMPLE BY DISSOLUTION
DE SA SURFACE, ET DISPOSITIF POUR SA MISE EN OEUVREOF ITS SURFACE, AND DEVICE FOR ITS IMPLEMENTATION
L'invention concerne le domaine de l'analyse des maté¬ riaux métalliques, plus particulièrement leur analyse par dissolu¬ tion progressive de leur surface.The invention relates to the field of analysis of metallic materials, more particularly their analysis by progressive dissolving of their surface.
Lorsqu'on étudie les différents.procédés de revêtement de produits métalliques par une ou plusieurs couches elles aussi métalliques (par exemple le revêtement de bandes d'acier par un alliage de zinc, cet alliage étant déposé par trempage ou électro¬ déposition) , il est important de pouvoir analyser le dépôt formé sur le produit de manière aussi fine que possible. En particulier il faut arriver à déceler au moins qualitativement les variations de la composition du dépôt entre sa surface libre et la surface du substrat métallique. A cet effet, il est connu d'utiliser un appa¬ reillage associant une cellule de dissolution électrochimique et un spectromètre, tel qu'un spectromètre d'émission à plasma à cou- plage inductif. L'échantillon dont la surface est à analyser est placé dans une cellule de petite dimension, laquelle est traversée par un electrolyte mis en mouvement par une pompe. L'electrolyte neuf entre dans la cellule et en ressort chargé de produits prove¬ nant de la dissolution de la surface libre de l'échantillon. Il est ensuite envoyé dans le spectromètre. Celui-ci détermine les intensités des rayonnements émis par l'electrolyte dans le plasma pour les longueurs d'onde caractéristiques des éléments que l'on désire détecter, ces intensités étant directement proportionnelles aux concentrations de ces éléments dans la solution. L'évolution de ces intensités au cours du temps, au fur et à mesure que se poursuit la dissolution de la surface, traduit le gradient de con¬ centration des divers éléments dans le revêtement depuis la surfa¬ ce initiale jusqu'au substrat métallique, voire dans le substrat lui-même si la dissolution est poursuivie encore plus avant. On peut, en particulier, chercher à déterminer la nature des phases qui se succèdent selon l'épaisseur du revêtement. A cet effet, il faut trouver un electrolyte qui puise dissoudre ces différentes phases les unes après les autres, mais suffisamment lentement pour qu'elles puissent être discriminées lors de l'analyse. Cette recherche d'un electrolyte convenable est souvent longue et fasti- dieuse, et implique que, pour un échantillon d'un type donné, l'expérimentateur ait déjà une idée relativement claire du résul¬ tat final avant de "débuter l'expérience définitive. Enfin, on ne peut que rarement être sûr d'avoir bien détecté toutes les phases en présence. Le but de l'invention est de proposer une méthode d'ana¬ lyse superficielle d'échantillons métalliques, toujours basée sur le couplage d'une cellule de dissolution électrochimique et d'un spectromètre, mais exempte des inconvénients cités ci-dessus, c'est-à-dire rendant fidèlement compte des gradients de concentra¬ tion des différents éléments du revêtement, et ne nécessitant pas de longs essais préliminaires avant l'analyse définitive.When we study the different methods of coating metallic products with one or more metallic layers (for example the coating of steel strips with a zinc alloy, this alloy being deposited by dipping or electro-deposition), it it is important to be able to analyze the deposit formed on the product as precisely as possible. In particular, it is necessary to detect at least qualitatively the variations in the composition of the deposit between its free surface and the surface of the metal substrate. To this end, it is known to use an apparatus associating an electrochemical dissolution cell and a spectrometer, such as a plasma emission spectrometer with inductive coupling. The sample whose surface is to be analyzed is placed in a small cell, which is crossed by an electrolyte set in motion by a pump. The new electrolyte enters the cell and leaves it charged with products from the dissolution of the free surface of the sample. It is then sent to the spectrometer. This determines the intensities of the radiation emitted by the electrolyte in the plasma for the wavelengths characteristic of the elements which it is desired to detect, these intensities being directly proportional to the concentrations of these elements in the solution. The evolution of these intensities over time, as the dissolution of the surface continues, reflects the gradient of concentration of the various elements in the coating from the initial surface to the metal substrate, or even in the substrate itself if the dissolution is continued even further. We can, in particular, seek to determine the nature of the successive phases according to the thickness of the coating. To this end, it an electrolyte must be found which can dissolve these different phases one after the other, but slowly enough so that they can be discriminated during the analysis. This search for a suitable electrolyte is often long and tedious, and implies that, for a sample of a given type, the experimenter already has a relatively clear idea of the final result before " starting the final experience Finally, one can only rarely be sure of having correctly detected all of the phases present. The object of the invention is to propose a method of surface analysis of metal samples, always based on the coupling of an electrochemical dissolution cell and a spectrometer, but free from the drawbacks mentioned above, that is to say faithfully accounting for the gradients of concentration of the various elements of the coating, and not requiring long preliminary tests before the final analysis.
A cet effet, l'invention a pour objet une méthode d'ana¬ lyse d'un échantillon métallique selon laquelle on réalise une dissolution de la surface dudit échantillon au moyen d'un électro- lyte s'écoulant sur ladite surface, et on détermine en continu, après le passage de l'electrolyte sur l'échantillon, la teneur de l'electrolyte en les divers constituants de ladite surface qu'il a dissous, caractérisée en ce qu'on détermine en continu le poten¬ tiel dudit échantillon par rapport à une électrode de référence plongée dans l'electrolyte, et on impose audit échantillon un paramètre électrique donné, de manière à provoquer la dissolution successive des différentes phases présentes à la surface de l'échantillon. Ce paramètre électrique peut être le potentiel de l'échantillon ou l'intensité du courant qui le traverse. L'invention a également pour objet un dispositif d'analy¬ se d'un échantillon métallique du type comprenant un réservoir contenant un electrolyte, une cellule de dissolution dont une paroi inclut une surface dudit échantillon, des moyens pour faire traverser ladite cellule par ledit electrolyte, et des moyens pour analyser en continu ledit electrolyte après sa traversée de ladi- te cellule, caractérisé en ce qu'il comprend des moyens pour mesu¬ rer en continu la différence de potentiel entre ledit échantillon et une électrode de référence plongée dans l'electrolyte à l'inté¬ rieur de ladite cellule, et des moyens pour imposer audit échan- tillon un potentiel déterminé par rapport à ladite électrode de référence, ou une intensité déterminée .pour le courant qui le tra¬ verse.To this end, the invention relates to a method of analysis of a metallic sample according to which a dissolution of the surface of said sample is carried out by means of an electrolyte flowing on said surface, and determines continuously, after the passage of the electrolyte over the sample, the content of the electrolyte in the various constituents of said surface which it has dissolved, characterized in that the potential of said sample is continuously determined relative to a reference electrode immersed in the electrolyte, and a given electrical parameter is imposed on said sample, so as to cause the successive dissolution of the different phases present on the surface of the sample. This electrical parameter can be the potential of the sample or the intensity of the current flowing through it. The invention also relates to a device for analyzing a metal sample of the type comprising a reservoir containing an electrolyte, a dissolution cell, one wall of which includes a surface of said sample, means for passing said cell through. electrolyte, and means for continuously analyzing said electrolyte after crossing the ladi- you cell, characterized in that it comprises means for mesu¬ rer continuously the potential difference between said sample and a reference electrode immersed in the electrolyte inte ¬ laughing of said cell, and means for imposing to said sample a potential determined with respect to said reference electrode, or a determined intensity. for the current flowing through it.
Préférentielleraent le dispositif comprend également une membrane échangeuse d'ions, séparant la cellule en deux comparti- ments.Preferably, the device also comprises an ion exchange membrane, separating the cell into two compartments.
Comme on l'aura compris, l'invention consiste à réaliser de manière successive et contrôlée la dissolution des différentes phases que comporte l'échantillon métallique au fur et à mesure qu'elles apparaissent lors de sa dissolution, et à déterminer la composition de ces phases d'après celle de l'electrolyte qui les a dissoutes.As will be understood, the invention consists in carrying out in a successive and controlled manner the dissolution of the different phases which the metal sample comprises as and when they appear during its dissolution, and in determining the composition of these phases according to that of the electrolyte which dissolved them.
L'invention sera mieux comprise à la lecture de la des¬ cription qui suit, celle-ci faisant référence aux figures annexées : - la figure 1 représente une cellule électrochimique selon l'invention avec ses annexes, vue de face en section selon II-II ;The invention will be better understood on reading the following description, which refers to the appended figures: FIG. 1 represents an electrochemical cell according to the invention with its appendices, front view in section along II- II;
- la figure 2 représente la même cellule vue de dessus en section I-I, les différentes pièces étant montrées écartées les unes des autres pour plus de clarté ;- Figure 2 shows the same cell seen from above in section I-I, the different parts being shown separated from each other for clarity;
- la figure 3 représente schématiquement l'ensemble de l'installation d'analyse ;- Figure 3 shows schematically the entire analysis installation;
- la figure 4 représente l'évolution au cours du temps d'une part de la différence de potentiel entre un échantillon et une électrode de référence, et d'autre part des intensités émises simultanément par les divers éléments dans un spectromètre lors d'une analyse réalisée par simple dissolution progressive de l'échantillon par l'electrolyte dans la cellule selon l'inven¬ tion ; - la figure 5 représente l'évolution des mêmes paramètres lors d'une analyse réalisée en imposant des potentiels de dissolu¬ tion constants successifs à l'échantillon placé dans la cellule selon l'invention. Un exemple de dispositif selon l'invention est représenté sur les figures 1, 2 et 3. La cellule comprend un corps 1 sensi¬ blement parallélépipédique dans lequel est ménagée une cavité cylindrique 2 ouverte sur la face supérieure du corps 1. Le corps 1 est également traversé par un canal 3 débouchant d'une part sur une face latérale 4 du corps 1, et d'autre part dans la cavité cylindrique 2. Contre la face latérale 4 est disposée une membrane poreuse 5, qui est préférentiellement une membrane échan- geuse d'ions, par exemple échangeuse d'anions. Celle-ci présente une superficie au moins suffisante pour obturer complètement l'orifice 6 du canal 3 débouchant sur la face latérale 4 du corps 1. La membrane 5 est plaquée contre la face latérale 4 au moyen d'une pièce 7 fixée de manière amovible au corps 1. Cette pièce 7 est percée de part en part par un orifice 8 qui prolonge l'orifice 6 du canal 3 du corps 1. Elle comprend également un canal 9 d'amenée de l'electrolyte à l'intérieur de l'orifice 8. Ce canal 9 débouche à l'extérieur de la cellule et est muni de moyens (non représentés sur la figure 1) pour sa connexion à une condui¬ te 23 reliée à un réservoir d'electrolyte 24. De préférence le canal 9 débouche dans la partie inférieure de l'orifice 8 de la pièce 7. Celle-ci comprend de même un canal 10 d'évacuation de l'electrolyte débouchant d'une part dans la partie supérieure de l'orifice 8 de la pièce 7, et d'autre part à l'extérieur de la cellule. Il est connecté à une conduite 27 reliée à un spectromè¬ tre 25 qui analyse en continu l'electrolyte chargé des matériaux qu'il a dissous à son passage sur l'échantillon 14. Cette disposi¬ tion de l'entrée et de la sortie de l'electrolyte dans la cellule permet une évacuation rapide des gaz formés pendant l'opération. La pièce 7 comprend enfin un logement 11 dans lequel peut être insérée une électrode de référence 12 dont l'extrémité 13 débouche dans l'orifice 8. Sur la face externe de la pièce 7 est plaqué l'échantillon de tôle métallique 14, de manière à obturer l'orifi¬ ce 8, avec la face à analyser tournée vers l'intérieur de la cel¬ lule. Pour limiter la formation de couches limites dans l'électro- lyte au voisinage de la surface de l'échantillon 14, les orifices des canaux 9 et 10 débouchant dans l'orifice 8 de la pièce 7 sont conformés de manière à diriger les écoulements de l'electrolyte vers la surface de l'échantillon 14. Un contact électrique 15 est relié à la face extérieure de l'échantillon 14. Toutes ces pièces sont maintenues solidaires et peuvent être séparées les unes des autres pour être changées. L'étanchéité de l'ensemble, lorsque la cellule est en fonctionnement et renferme suffisamment d'electro¬ lyte pour remplir le canal 3, est assurée par deux joints 16 et 17, placés respectivement entre le corps 1 et la membrane 5 et entre la pièce 7 et l'échantillon 10. L'installation comprend éga¬ lement une électrode 18, de préférence en platine, plongée dans la cavité cylindrique 2. L'électrode de platine 18, le contact élec¬ trique 15 et l'électrode de référence 12 sont reliés à un poten¬ tiostat 19, respectivement par des connexions 20, 21, 22. Le potentiostat 19 permet de maintenir une différence de potentiel constante et connue entre l'électrode de platine 18, placée en cathode, et l'échantillon 14 à analyser, placé en anode, et de mesurer la différence de potentiel entre l'échantillon 14 et l'électrode de référence 12. L'electrolyte est mis en mouvement grâce à une pompe 25 insérée entre la cellule 1 et le spectromè¬ tre 25.- Figure 4 shows the evolution over time on the one hand of the potential difference between a sample and a reference electrode, and on the other hand of the intensities emitted simultaneously by the various elements in a spectrometer during a analysis performed by simple progressive dissolution of the sample by the electrolyte in the cell according to the invention; - Figure 5 shows the evolution of the same parameters during an analysis by imposing successive constant dissolu¬ tion potentials on the sample placed in the cell according to the invention. An example of a device according to the invention is shown in FIGS. 1, 2 and 3. The cell comprises a body 1 which is substantially parallelepiped in which a cylindrical cavity 2 is formed, open on the upper face of the body 1. The body 1 is also traversed by a channel 3 opening on the one hand on a lateral face 4 of the body 1, and on the other hand in the cylindrical cavity 2. Against the lateral face 4 is arranged a porous membrane 5, which is preferably an exchanging membrane ion gayer, for example anion exchange. This has an area at least sufficient to completely seal the orifice 6 of the channel 3 opening onto the lateral face 4 of the body 1. The membrane 5 is pressed against the lateral face 4 by means of a piece 7 detachably fixed to the body 1. This part 7 is pierced right through by an orifice 8 which extends the orifice 6 of the channel 3 of the body 1. It also includes a channel 9 for supplying the electrolyte inside the orifice 8. This channel 9 opens out to the outside of the cell and is provided with means (not shown in FIG. 1) for its connection to a condui¬ te 23 connected to an electrolyte reservoir 24. Preferably channel 9 opens into the lower part of the orifice 8 of the part 7. This likewise comprises a channel 10 for discharging the electrolyte opening out on the one hand into the upper part of the orifice 8 of the part 7, and on the other hand outside the cell. It is connected to a pipe 27 connected to a spectrometer 25 which continuously analyzes the electrolyte charged with the materials which it has dissolved in its passage over the sample 14. This arrangement of the inlet and the outlet of the electrolyte in the cell allows rapid evacuation of the gases formed during the operation. The part 7 finally comprises a housing 11 into which a reference electrode 12 can be inserted, the end 13 of which opens out in the orifice 8. On the external face of the part 7 is pressed the sheet metal sample 14, so as to close the orifice 8, with the face to be analyzed turned towards the inside of the cell. . To limit the formation of boundary layers in the electrolyte in the vicinity of the surface of the sample 14, the orifices of the channels 9 and 10 opening into the orifice 8 of the part 7 are shaped so as to direct the flows of the electrolyte towards the surface of the sample 14. An electrical contact 15 is connected to the external face of the sample 14. All these parts are held together and can be separated from one another to be changed. The tightness of the assembly, when the cell is in operation and contains enough electro¬ lyte to fill the channel 3, is ensured by two seals 16 and 17, placed respectively between the body 1 and the membrane 5 and between the piece 7 and the sample 10. The installation also includes an electrode 18, preferably made of platinum, immersed in the cylindrical cavity 2. The platinum electrode 18, the electrical contact 15 and the reference electrode 12 are connected to a poten¬ tiostat 19, respectively by connections 20, 21, 22. The potentiostat 19 makes it possible to maintain a constant and known potential difference between the platinum electrode 18, placed as a cathode, and the sample 14 to be analyzed, placed at the anode, and to measure the potential difference between the sample 14 and the reference electrode 12. The electrolyte is set in motion by a pump 25 inserted between the cell 1 and the spectrometer 25 .
A titre d'exemple, le compartiment anodiqua défini par l'échantillon 14 et la membrane échangeuse d'anions 5 peut avoir un volume d'environ 0,15 ml voire moins, et la surface de l'échan- tillon 14 exposée à l'electrolyte est de l'ordre de 0,5 cm2. L'electrolyte circule dans l'installation avec un débit de l'ordre de 2 ml/min. Le compartiment cathodique a un volume d'environ 10 ml. L'electrolyte de platine a une surface de 10 cm2. Dans l'expérience qui va être décrite, l'électrode de référence est un fil d'argent de 0,5 mm de diamètre revêtu par électrodéposition d'une couche de chlorure d'argent.By way of example, the anodic compartment defined by the sample 14 and the anion exchange membrane 5 may have a volume of approximately 0.15 ml or even less, and the surface of the sample 14 exposed to the electrolyte is of the order of 0.5 cm 2 . The electrolyte circulates in the installation with a flow rate of the order of 2 ml / min. The cathode compartment has a volume of approximately 10 ml. The platinum electrolyte has an area of 10 cm 2 . In the experiment which will be described, the reference electrode is a silver wire 0.5 mm in diameter coated by electrodeposition with a layer of silver chloride.
Le rôle de la membrane échangeuse d'anions 5 est triple. D'une part, elle permet de réaliser facilement- un compartiment anodique de faible volume, ce qui va de pair avec un temps de séjour réduit pour l'electrolyte. On diminue ainsi le temps de réaction de l'appareillage, on augmente son pouvoir de résolution dans sa capacité à discriminer les différentes phases de l'échan¬ tillon à analyser, et on améliore l'homogénéité de la composition de l'electrolyte dans le compartiment anodique. D'autre part, la membrane 5 permet d'isoler les compartiments anodique et cathodi¬ que tout en laissant passer le courant électrique, et les réac¬ tions chimiques qui peuvent se produire dans le compartiment cathodique (dans l'exemple suivant, un dégagement d'hydrogène et un dépôt d'ions métalliques) ne viennent ainsi pas perturber les mesures. Enfin, elle empêche les cations en provenance de l'échan¬ tillon de migrer dans le compartiment cathodique, ce qu'une simple membrane poreuse en pourrait assurer. On s'assure ainsi que tous les produits issus de la dissolution de l'échantillon sont bien évacués vers le spectromètre 25. Sans être à proprement parler indispensable, cette membrane 5 est donc d'une très grande utili¬ té, d'autant plus que la cellule est de petite taille. On peut ainsi réaliser la dissolution de l'échantillon sur une très faible portion de sa surface. On va maintenant décrire un exemple d'analyse conduite à l'aide de l'appareillage qui vient d'être décrit. L'échantillon est un échantillon de tôle d'acier galvanisé de type "Extra- gai ®", préparé de manière classique dans un bain de zinc conte¬ nant 0,16 % d'aluminium et 0,04 % de plomb. Le spectromètre est un spectromètre d'émission optique à plasma à couplage inductif, détectant les longueurs d'ondes suivantes pour les différents élé¬ ments à analyser : pour le zinc 3302,6 Â, pour le fer 2599,4 Â, pour l'aluminium 3961,5 Â. Ce type de spectromètre est préféren- tiellement choisi pour la rapidité de sa réponse. L'electrolyte est une solution d'acide chlorhydrique 1,2 M. Dans un premier temps, on peut utiliser la cellule selon l'invention comme s'il s'agissait d'une cellule de dissolution classique, c'est-à-dire en ne connectant pas la cathode 18 au potentiostat 19. En revanche, on utilise celui-ci pour mesurer la différence de potentiel qui s'établit spontanément entre l'échan¬ tillon 14 et l'électrode de référence 12 au fur et à mesure que l'échantillon 14 est dissous par l'electrolyte, opération que l'on n'effectue habituellement pas dans les cellules classiques. La figure 4 montre les évolutions au cours du temps, d'une part de la différence de potentiel E mesurée entre l'électrode de référen¬ ce 12 et l'échantillon 14, traduite par la courbe 28, et d'autre part des intensités d'émission du spectromètre 25 correspondant aux divers éléments recherchés : le zinc correspond à la cour¬ be 29, le fer à la courbe 30 et l'aluminium à la courbe 31. Ces intensités sont exprimées en unités arbitraires, et les échelles sont différentes pour chaque élément : la hauteur de chaque pic desdites courbes est bien proportionnelle à •la concentration dans l'electrolyte de l'élément qu'il représente, mais les hauteurs relatives des différents pics ne sont pas représentatives des pro- portions respectives des différents éléments dans le revêtement de l'échantillon 14. La courbe 28 indique la présence de deux phases dans le revêtement, dont les dissolutions respectives imposent à l'échantillon 14 des potentiels de l'ordre de — 940 mV environ pour une première phase, et de - 800 à - 650 mV pour la deuxième phase. Les courbes 29, 30 et 31 indiquent d'autre part que la' pre¬ mière phase est composée de zinc et d'une certaine quantité d'alu¬ minium vraisemblablement très faible, et que la deuxième phase est un alliage de fer et d'aluminium. Après dissolution de cette deuxième phase, la différence de potentiel E devient stable et on n'observe pas de réaction qui pourrait correspondre à une dissolu¬ tion du substrat d'acier. Une telle réaction, dans les conditions de 1*expérience, ne pourrait se produire qu'en présence d'un cata¬ lyseur. Précisons enfin que l'étalement dans le temps des diffé¬ rents pics d'intensité d'émission I n'est pas strictement propor- tionnel à l'épaisseur des différentes phases : il est aussi fonc¬ tion de leur vitesse de dissolution qui peut être différente pour chacune d'elles.The role of the anion exchange membrane 5 is threefold. On the one hand, it makes it easy to produce a low-volume anode compartment, which goes hand in hand with a reduced residence time for the electrolyte. The reaction time of the apparatus is thus reduced, its resolving power is increased in its capacity to discriminate the different phases of the sample to be analyzed, and the homogeneity of the composition of the electrolyte is improved in the anode compartment. On the other hand, the membrane 5 makes it possible to isolate the anode and cathode compartments while allowing the electric current to pass, and the chemical reactions which can occur in the cathode compartment (in the following example, a release hydrogen and a deposit of metal ions) do not interfere with the measurements. Finally, it prevents cations from the sample from migrating into the cathode compartment, which a simple porous membrane could do. This ensures that all the products resulting from the dissolution of the sample are well evacuated to the spectrometer 25. Without being strictly speaking essential, this membrane 5 is therefore very useful, all the more that the cell is small. It is thus possible to dissolve the sample over a very small portion of its surface. We will now describe an example of analysis carried out using the apparatus which has just been described. The sample is a sample of galvanized steel sheet of the "Extragai ®" type, conventionally prepared in a zinc bath containing 0.16% aluminum and 0.04% lead. The spectrometer is an inductively coupled plasma optical emission spectrometer, detecting the following wavelengths for the various elements to be analyzed: for zinc 3302.6 Â, for iron 2599.4 Â, for aluminum 3961.5 Â. This type of spectrometer is preferably chosen for the speed of its response. The electrolyte is a 1.2 M hydrochloric acid solution. Initially, the cell according to the invention can be used as if it were a conventional dissolution cell, that is to say by not connecting the cathode 18 to the potentiostat 19. On the other hand, this is used to measure the potential difference which is established spontaneously between the sample 14 and the reference electrode 12 as the sample 14 is dissolved by the electrolyte, an operation which l 'it is not usually done in conventional cells. FIG. 4 shows the changes over time, firstly of the potential difference E measured between the reference electrode 12 and the sample 14, translated by the curve 28, and secondly of the intensities emission of the spectrometer 25 corresponding to the various elements sought: zinc corresponds to the curve 29, iron to the curve 30 and aluminum to the curve 31. These intensities are expressed in arbitrary units, and the scales are different for each element: the height of each peak of said curves is well proportional to • the concentration in the electrolyte of the element it represents, but the relative heights of the different peaks are not representative of the respective proportions of the different elements in the coating of the sample 14. The curve 28 indicates the presence of two phases in the coating, the respective dissolutions of which impose on the sample 14 potentials of the order d e - approximately 940 mV for the first phase, and from - 800 to - 650 mV for the second phase. The curves 29, 30 and 31 indicate further that the 'pre¬ Mière phase is composed of zinc and a certain amount of alu¬ minium likely to be very low, and that the second phase is an alloy of iron and 'aluminum. After dissolution of this second phase, the potential difference E becomes stable and no reaction is observed which could correspond to a dissolution of the steel substrate. Such a reaction, under the conditions of the experiment, could only occur in the presence of a catalyst. Finally, note that the spread over time of the different peaks of emission intensity I is not strictly proportional tional to the thickness of the different phases: it is also a function of their dissolution rate which may be different for each of them.
L'expérience précédente permet d'avoir une idée approxi- mative des différences de potentiel E correspondant aux dissolu¬ tions des principales phases du revêtement. Ces informations sont mises à profit pour exécuter ensuite l'analyse fine des différen¬ tes phases en utilisant le dispositif complet précédemment décrit. L'électrode de platine 18 est alors connectée en cathode au poten- tiostat 19 de manière à pouvoir maintenir ente elle et l'échantil¬ lon 14 des différences de potentiel successives telles qu'elles correspondent aux potentiels de dissolution des différentes phases que l'on recherche. On a également la possibilité d'imposer d'au¬ tres potentiels pour chercher à discriminer d'autres phases que l'expérience préliminaire précédemment décrite n'aurait pas mises en évidence.The previous experience gives an approximate idea of the potential differences E corresponding to the dissolu¬ tions of the main phases of the coating. This information is used to then carry out a detailed analysis of the different phases using the complete device described above. The platinum electrode 18 is then connected as a cathode to the potentiometer 19 so as to be able to maintain between it and the sample 14 successive potential differences such that they correspond to the dissolution potentials of the different phases that the we are looking for. There is also the possibility of imposing other potentials in order to seek to discriminate other phases that the preliminary experience previously described would not have demonstrated.
La figure 5 montre les évolutions au cours du temps des mêmes paramètres que la figure précédente : la courbe 28 représen¬ te la différence de potentiel E entre l'électrode de référence 12 et l'échantillon 14, les courbes 29, 30 et 31 représentent les intensités d'émission I du zinc, du fer et de l'aluminium dans le spectromètre. L'expérience se déroule de la façon suivante : on laisse d'abord le circuit électrique ouvert pendant 50 s, et un potentiel de - 1044 mV à l'anode (l'échantillon 14) s'établit. Puis on impose à l'anode un potentiel de - 944 mV. On observe alors la dissolution d'une première phase comportant essentielle¬ ment du zinc avec une très petite quantité d'aluminium. Il s'agit manifestement de la dissolution de la couche extérieure du revête¬ ment, où on n'observe pas de fer. Après 700 s d'expérience, les intensités émises reviennent au niveau zéro, ce qui montre la fin de la dissolution de cette première phase. On impose ensuite un potentiel de - 740 mV. On n'observe alors plus de dissolution de zinc, mais une dissolution simultanée de fer et d'aluminium (NB : l'absence totale de zinc constatée est peut être imputable au manque de sensibilité de la longueur d'onde utilisée pour sa détection ; le spectromètre utilisé ne permettait pas d'en choisir une autre) . La dissolution de cette phase se poursuit pendant 250 s environ. Puis on impose un potentiel de - 500 mV, et on observe alors une dissolution simultanée de fer et d'aluminium, avec une présence d'aluminium sensiblement inférieure à ce qu'elle était dans la phase précédente. La présence de cette troisième phase n'avait pu être détectée lors de l'expérience préliminaire. Des expériences et examens supplémentaires sont actuellement en cours pour déterminer l'origine et la nature de cette troisième phase. On observe également que l'intensité d'émission du fer ne revient pas exactement à son niveau initial après la dissolution de la troisième phase, ce qui tend à montrer un début de dissolu¬ tion du substrat en acier. L'expérience s'achève par une période de maintien du potentiel à - 376 V, pendant laquelle on observe la dissolution du substrat en acier, comme en témoigne l'intensité d'émission élevée du fer et l'absence d'émission du zinc et de l'aluminium. L'expérience préliminaire, rappelons-le, n'avait pas permis de parvenir à ce stade. Une analyse quantitative des différentes phases est pos¬ sible en intégrant les profils de dissolution obtenus à chaque potentiel et en étalonnant l'échelle d'intensités avec des solu¬ tions standard de zinc, de fer et d'aluminium. A titre d'exemple, une telle analyse conduite sur la phase dissoute à - 740 mV de l'exemple précédent montre que le rapport molaire des concentra¬ tions en aluminium et en fer y est de 1,51 ± 0,06, et qu'il est de 0,2 ± 0,02 pour la phase dissoute à - 500 mV.FIG. 5 shows the changes over time of the same parameters as the previous figure: the curve 28 represents the potential difference E between the reference electrode 12 and the sample 14, the curves 29, 30 and 31 represent the emission intensities I of zinc, iron and aluminum in the spectrometer. The experiment proceeds as follows: the electrical circuit is first left open for 50 s, and a potential of - 1044 mV at the anode (sample 14) is established. Then we impose on the anode a potential of - 944 mV. We then observe the dissolution of a first phase essentially comprising zinc with a very small amount of aluminum. This is obviously the dissolution of the outer layer of the coating, where no iron is observed. After 700 s of experience, the intensities emitted return to zero, which shows the end of the dissolution of this first phase. We then impose a potential of - 740 mV. We no longer observe any dissolution of zinc, but a simultaneous dissolution of iron and aluminum (NB: the total absence of zinc observed may be due to the lack of sensitivity of the wavelength used for its detection; the spectrometer used did not allow to choose another). The dissolution of this phase continues for approximately 250 s. Then a potential of - 500 mV is imposed, and a simultaneous dissolution of iron and aluminum is observed, with the presence of aluminum significantly lower than it was in the previous phase. The presence of this third phase could not have been detected during the preliminary experiment. Additional experiments and examinations are currently underway to determine the origin and nature of this third phase. It is also observed that the intensity of emission of iron does not return exactly to its initial level after the dissolution of the third phase, which tends to show a beginning of dissolu¬ tion of the steel substrate. The experiment ends with a period of maintaining the potential at - 376 V, during which the dissolution of the steel substrate is observed, as evidenced by the high emission intensity of iron and the absence of emission of zinc. and aluminum. It should be remembered that the preliminary experience did not allow this stage to be reached. A quantitative analysis of the different phases is possible by integrating the dissolution profiles obtained for each potential and by calibrating the intensity scale with standard solutions of zinc, iron and aluminum. By way of example, such an analysis carried out on the dissolved phase at −740 mV of the previous example shows that the molar ratio of the aluminum and iron concentrations therein is 1.51 ± 0.06, and that qu '' it is 0.2 ± 0.02 for the dissolved phase at - 500 mV.
Comme on l'a vu, l'appareillage selon l'invention permet de réaliser une analyse des phases du revêtement sensiblement plus fine que par la méthode classique de dissolution sans contrôle du potentiel de l'échantillon, même lorsque cette méthode est amélio¬ rée par la mesure du potentiel de l'échantillon. De plus, alors qu'avec la méthode classique, les différentes phases étaient atta¬ quées et dissoutes les unes après les autres sans interruption très marquée entre elles, l'invention permet d'interrompre aisé¬ ment l'expérience après la dissolution d'une phase donnée, de manière à permettre l'analyse microscopique des alliages interfa¬ ciaux. Enfin, notons que la précision de cette méthode d'analyse est beaucoup moins tributaire du choix de l'electrolyte que ne l'est la méthode de dissolution classique sans potentiel imposé. Avant d'effectuer une analyse fine significative des différentes phases, il n'est donc pas nécessaire de procéder à un grand nombre d1expériences préliminaires fastidieuses. II est également possible de procéder en.n'effectuant pas l'expérience préliminaire sans potentiel imposé, mais en imposant d'entrée à l'échantillon un potentiel initial donné. On observe alors s'il se produit une dissolution. Dans l'affirmative on attend la fin de la dissolution pour procéder à l'abaissement du potentiel imposé d'une valeur déterminée. Dans la négative, on abaisse immédiatement ce potentiel de ladite valeur déterminée et on observe l'éventuelle dissolution qui se produit. En diminuant le potentiel par pas successifs jusqu'à une dissolution de l'échantillon jugée suffisante, on peut déceler toutes les phases qui constituent sa surface si ces pas ont été convenablement choisis.As we have seen, the apparatus according to the invention makes it possible to carry out an analysis of the phases of the coating substantially finer than by the conventional method of dissolution without checking the potential of the sample, even when this method is improved. by measuring the potential of the sample. In addition, whereas with the conventional method, the different phases were attacked and dissolved one after the other without interruption very marked between them, the invention makes it possible to easily interrupt the experiment after the dissolution of a given phase, so as to allow microscopic analysis of the interfa¬ cial alloys. Finally, note that the accuracy of this analysis method is much less dependent on the choice of electrolyte than is the conventional dissolution method with no imposed potential. Before making a significant fine analysis of the different phases, it is not necessary to perform a large number of 1 tedious preliminary experiments. It is also possible to proceed by not carrying out the preliminary experiment without an imposed potential, but by imposing on the sample a given initial potential. It is then observed whether a dissolution occurs. If so, we await the end of the dissolution before proceeding to lower the imposed potential by a determined value. If not, this potential is immediately lowered by said determined value and the possible dissolution that occurs is observed. By decreasing the potential in successive steps until a dissolution of the sample deemed sufficient, one can detect all the phases which constitute its surface if these steps have been suitably chosen.
En variante, on peut remplacer le potentiostat 19 par un intensiostat, de manière à imposer une intensité donnée au courant qui traverse l'échantillon. Dans ces conditions, on peut suivre l'évolution de la composition de l'electrolyte au fur et à mesure de la dissolution de l'échantillon, tout en la mettant en relation avec les potentiels pris successivement par l'échantillon et mesu¬ rés par rapport à l'électrode de référence.Alternatively, the potentiostat 19 can be replaced by an intensiostat, so as to impose a given intensity on the current flowing through the sample. Under these conditions, the evolution of the composition of the electrolyte can be followed as the sample dissolves, while relating it to the potentials taken successively by the sample and measured by relative to the reference electrode.
De manière générale, le contrôle du potentiel de dissolu- tion ou de l'intensité du courant permet de contrôler la sélecti¬ vité de la dissolution et sa cinétique.In general, controlling the dissolution potential or the intensity of the current makes it possible to control the selectivity of the dissolution and its kinetics.
Bien entendu, l'invention n'est nullement limitée à l'exemple qui vient d'être décrit. En particulier, d'autres mor¬ phologies de la cellule sont imaginables, de manière à analyser des échantillons de formes diverses, et le spectromètre d'émission à plasma couplé inductivement peut être remplacé par tout autre type d'appareil capable d'analyser l'electrolyte en continu. De même l'invention est applicable à tout échantillon métallurgique dont on désire connaître la composition superficielle, qu'il com¬ porte ou non un revêtement métallique distinct du métal de base. En particulier, si on est en présence d'un échantillon d'un allia¬ ge de plusieurs métaux, il est parfaitement possible de déterminer la répartition de ces métaux sur la profondeur de l'échantillon en réalisant la dissolution progressive de celui-ci. Of course, the invention is in no way limited to the example which has just been described. In particular, other cell morphologies are imaginable, so as to analyze samples of various shapes, and the inductively coupled plasma emission spectrometer can be replaced by any other type of device capable of continuously analyzing the electrolyte. Likewise, the invention is applicable to any metallurgical sample for which it is desired to know the surface composition, whether or not it has a metallic coating separate from the base metal. In particular, if there is a sample of an alloy of several metals, it is perfectly possible to determine the distribution of these metals over the depth of the sample by carrying out the gradual dissolution of the latter.

Claims

REVENDICATIONS
1) Méthode d'analyse d'un échantillon métallique selon laquelle on réalise une dissolution de la surface dudit échantil- Ion au moyen d'un electrolyte s'écoulant sur ladite surface, et on détermine en continu, après le passage de l'electrolyte sur l'échantillon, la teneur de l'electrolyte en les divers consti¬ tuants de ladite surface qu'il a dissous, caractérisée en ce qu'on détermine en continu, le potentiel dudit échantillon par rapport à une électrode de référence plongée dans l'electrolyte, et on impo¬ se audit échantillon un paramètre électrique donné, de manière à provoquer la dissolution successive des différentes phases présen¬ tes à la surface de l'échantillon.1) Method of analysis of a metallic sample according to which a dissolution of the surface of said sample is carried out by means of an electrolyte flowing on said surface, and a determination is made continuously, after the passage of the electrolyte on the sample, the content of the electrolyte in the various constituents of said surface which it has dissolved, characterized in that the potential of said sample is continuously determined relative to a reference electrode immersed in the electrolyte, and a given electrical parameter is imposed on said sample, so as to cause the successive dissolution of the different phases present on the surface of the sample.
2) Méthode d'analyse selon la revendication 1, caractéri¬ sée en ce qu'on impose audit échantillon des potentiels correspon¬ dants aux potentiels de dissolution des différentes phases présen¬ tes à la surface de l'échantillon au fur et à mesure de sa disso¬ lution.2) Analysis method according to claim 1, characterized in that it imposes on the sample potentials corresponding to the dissolution potentials of the different phases present on the surface of the sample as and when its dissolution.
3) Méthode d'analyse selon la revendication 1, caractéri¬ sée en ce qu'on impose audit échantillon l'intensité du courant électrique qui le traverse.3) Method of analysis according to claim 1, characterized in that the intensity of the electric current flowing through it is imposed on said sample.
4) Dispositif d'analyse d'un échantillon métallique (14) du type comprenant un réservoir (24) contenant un electrolyte, une cellule de dissolution (1) dont une paroi inclut une surface dudit échantillon (14), des moyens (9, 10, 23, 26, 27) pour faire tra¬ verser ladite cellule (1) par ledit electrolyte, et des moyens (25) pour analyser en continu ledit electrolyte après sa traversée de ladite cellule (1), caractérisé en ce qu'il comprend des moyens pour mesurer en continu la différence de potentiel entre ledit échantillon (14) et une électrode (12) de référence plongée dans l'electrolyte à l'intérieur de ladite cellule (1), et des moyens pour imposer audit échantillon un potentiel déterminé par rapport à ladite électrode de référence.4) Device for analyzing a metal sample (14) of the type comprising a reservoir (24) containing an electrolyte, a dissolution cell (1), one wall of which includes a surface of said sample (14), means (9, 10, 23, 26, 27) for causing said cell (1) to flow through said electrolyte, and means (25) for continuously analyzing said electrolyte after it has passed through said cell (1), characterized in that it comprises means for continuously measuring the potential difference between said sample (14) and a reference electrode (12) immersed in the electrolyte inside said cell (1), and means to impose on said sample a determined potential with respect to said reference electrode.
5) Dispositif selon la revendication 4, caractérisé en ce que lesdits moyens pour imposer audit échantillon (14) un poten¬ tiel déterminé par rapport à ladite électrode (12) de référence comprennent un potentiostat (19) relié par des connexions électri¬ ques (20, 21, 22) à une électrode (18) plongée dans l'electrolyte contenu dans la cellule (1), à l'échantillon (14) et à l'électrode de référence (12).5) Device according to claim 4, characterized in that said means for imposing on said sample (14) a potential determined relative to said reference electrode (12) comprise a potentiostat (19) connected by electrical connections ( 20, 21, 22) to an electrode (18) immersed in the electrolyte contained in the cell (1), to the sample (14) and to the reference electrode (12).
6) Dispositif d'analyse d'un échantillon métallique (14) du type comprenant un réservoir (24) contenant un electrolyte, une cellule de dissolution (1) dont une paroi inclut une surface dudit échantillon (14), des moyens (9, 10, 23, 26, 27) pour faire tra¬ verser ladite cellule (1) par ledit electrolyte, et des moyens (25) pour analyser en continu ledit electrolyte après sa traversée de ladite cellule (1), caractérisé en ce qu'il comprend des moyens pour mesurer en continu la différence de potentiel entre ledit échantillon (14) et une électrode (12) de référence plongée dans l'electrolyte à l'intérieur de ladite cellule (1) et des moyens pour faire traverser ledit échantillon par un courant d'intensité constante.6) Device for analyzing a metallic sample (14) of the type comprising a reservoir (24) containing an electrolyte, a dissolution cell (1), one wall of which includes a surface of said sample (14), means (9, 10, 23, 26, 27) for causing said cell (1) to flow through said electrolyte, and means (25) for continuously analyzing said electrolyte after it has passed through said cell (1), characterized in that it comprises means for continuously measuring the potential difference between said sample (14) and a reference electrode (12) immersed in the electrolyte inside said cell (1) and means for passing said sample through constant intensity current.
7) Dispositif selon l'une des revendications 4 à 6, caractérisé en ce que ladite cellule (1) comporte une membrane poreuse (5) intercalée entre ledit échantillon (14) et ladite électrode (18) et divisant ladite cellule (1) en deux comparti¬ ments.7) Device according to one of claims 4 to 6, characterized in that said cell (1) comprises a porous membrane (5) interposed between said sample (14) and said electrode (18) and dividing said cell (1) into two compartments.
8) Dispositif selon la revendication 7, caractérisé en ce que ladite membrane poreuse, (5) est une membrane échangeuse d'ions. 9) Dispositif selon la revendication 8, caractérisé en ce que ladite membrane poreuse (5) est une membrane échangeuse d'anions. 8) Device according to claim 7, characterized in that said porous membrane (5) is an ion exchange membrane. 9) Device according to claim 8, characterized in that said porous membrane (5) is an anion exchange membrane.
PCT/FR1993/000277 1992-03-25 1993-03-19 Method of analysis of a metallic sample by dissolving the surface thereof and device for carrying out said method WO1993019365A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR92/03782 1992-03-25
FR9203782A FR2689244A1 (en) 1992-03-25 1992-03-25 Method of analysis of a metallic sample by dissolution of its surface, and device for its implementation.

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WO1993019365A1 true WO1993019365A1 (en) 1993-09-30

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EP0813053A1 (en) * 1996-06-10 1997-12-17 Honda Giken Kogyo Kabushiki Kaisha Electrolytic test machine

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JP3778037B2 (en) * 2000-12-05 2006-05-24 Ｊｆｅスチール株式会社 Determination method of alloy phase in plating layer

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US3900375A (en) * 1973-12-13 1975-08-19 Texas Instruments Inc Electrolytic separation of metals
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DE2658357A1 (en) * 1976-12-23 1978-06-29 Fischer Gmbh & Co Helmut Electrolytic measurement of tin plating thickness - uses two hemispherical shells enclosing plate, with auxiliary electrode mounted clear of gas stream
CA1175904A (en) * 1982-04-02 1984-10-09 Stelco Inc. Metal analysis for acid-soluble elements
FR2579326A1 (en) * 1985-03-22 1986-09-26 Minas Gerais Siderurg Improvements to apparatuses intended for the rapid dissolving of metal alloy samples for chemical analysis
EP0326427A2 (en) * 1988-01-29 1989-08-02 The Dow Chemical Company Process for the recovery of alkanolamines from their heat-stable salts formed in alkanolamines sorbent solutions
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GB1434199A (en) * 1972-10-19 1976-05-05 Wilkinson Sword Ltd Selective electrolytic dissolution of predetermined metals
US3900375A (en) * 1973-12-13 1975-08-19 Texas Instruments Inc Electrolytic separation of metals
DE2658357A1 (en) * 1976-12-23 1978-06-29 Fischer Gmbh & Co Helmut Electrolytic measurement of tin plating thickness - uses two hemispherical shells enclosing plate, with auxiliary electrode mounted clear of gas stream
CA1175904A (en) * 1982-04-02 1984-10-09 Stelco Inc. Metal analysis for acid-soluble elements
FR2579326A1 (en) * 1985-03-22 1986-09-26 Minas Gerais Siderurg Improvements to apparatuses intended for the rapid dissolving of metal alloy samples for chemical analysis
EP0326427A2 (en) * 1988-01-29 1989-08-02 The Dow Chemical Company Process for the recovery of alkanolamines from their heat-stable salts formed in alkanolamines sorbent solutions
WO1992021792A1 (en) * 1991-05-30 1992-12-10 Sikel N.V. Method and apparatus for continuously preparing a steel strip having an electrolytically deposited coating layer

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0813053A1 (en) * 1996-06-10 1997-12-17 Honda Giken Kogyo Kabushiki Kaisha Electrolytic test machine
US6080293A (en) * 1996-06-10 2000-06-27 Honda Giken Kogyo Kabushiki Kaisha Electrolytic test machine

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FR2689244A1 (en) 1993-10-01

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