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
  • G01N27/423—Coulometry

Definitions

• the invention relates to the field of methods and devices for analyzing the level of cleanliness and / or activation of a surface of an electrically conductive part.
• the evaluation of the cleanliness of a surface of a room is particularly useful if it is desired to apply to this surface a surface treatment or a coating layer whose quality could be affected by a lack of cleanliness.
• the measure of cleanliness makes it possible for example to qualify the preparation of the part before the surface treatment. It is noted that a lack of cleanliness of the surface may lead to embrittlement of the coating layer formed on the part and in some cases to embrittlement of the part itself.
• An object of the present invention is a method and / or device for quantifying the cleanliness and / or the activation of a surface of a part.
• the invention relates to an analysis method for quantifying a level of cleanliness and / or activation of a surface of an electrically conductive part.
• This method is essentially characterized in that it comprises:
• activation is the ability of an electrically conductive surface to interact with an electrolytic environment.
• the greater this activation the better the electrochemical surface reactions.
• a well-activated surface will improve the Faraday efficiency (saving electricity, saving time) and lead to a better adhesion of an electrolytic deposit.
• the part whose level of cleanliness and / or activation is to be quantified must be electrically conductive at least at the level of the surface whose cleanliness and / or activation is quantified.
• the method according to the invention makes use of the physical properties of the COTTRELL law, which is an electrochemical law.
• the method of the invention thus makes it possible objectively to quantify the state of cleanliness and / or activation, for example to decide objectively the type of treatment to which the part must be subjected.
• the invention makes it possible to adjust the level of cleanliness and / or activation desired according to the field of use of the part.
• a part intended for a light environment may accept a level of cleanliness and / or activation less than a piece intended for a constraining environment.
• the invention also relates to methods of producing an element such as an aircraft mechanical element using any of the embodiments of the method of analysis described in this patent application.
• a level of cleanliness and / or activation of a surface of the part thus prepared is quantified by implementing the analysis method according to any of the modes described in the present application; then
• the element is subjected to a complementary operation of treatment of its surface
• the element is subjected again to the operation of surface preparation.
• additional operation of surface treatment is meant an operation to confer on the element an additional characteristic such as an anticorrosion treatment or an improvement of the hardness of the element or a surface protection.
• a complementary operation may consist in the application of a layer of a coating on the element such as a layer of paint, a layer of metal coating deposited via an electrolytic bath, or a coating layer deposited by spraying. a powdery mixture.
• This mode makes it possible to evaluate the cleanliness and / or the activation of the element that is produced by using several pieces / test pieces of cleanliness measurement.
• the cleanliness / activation of the element is thus evaluated without having to perform a test directly on the element. This limits the risk of polluting / degrading the element during the analysis.
• This second embodiment of the production method of the element is essentially characterized in that: the element and several parts are subjected to the same surface preparation operation (typically, a surface preparation operation is a cleaning or degreasing operation carried out for example in a bath containing detergent products); and
• the method of analysis according to any one of the modes described in the present application is used to quantify for each piece thus prepared a level of cleanliness and / or surface activation, and then
• the element is subjected to a complementary operation of treatment of its surface
• the implementation of the surface treatment operation is conditioned on the prior achievement of an estimated level of cleanliness and / or activation of the element via measurements made on the pieces / specimens.
• the surface treatment performed on the element is of better quality than if it had not previously measured / evaluated cleanliness and / or 1 activation.
• the surface treatment operation consists in applying a layer
• this layer will be applied once the level of cleanliness and / or estimated activation of the element is reached.
• this estimated level is not reached, then a complementary operation of preparation of the surface of the element is carried out until the level of cleanliness and / or required activation is achieved to perform the complementary surface treatment operation.
• the invention finally relates to a device for quantifying a level of cleanliness and / or activation of a surface of an electrically conductive part.
• This device is essentially characterized in that it comprises:
• sealing means extending at the periphery of an opening of the enclosure, these sealing means being arranged to provide a seal between an inner zone of the enclosure for containing the electrolyte and a portion of the electrically conductive part containing said surface disposed opposite an inner zone of the enclosure;
• a counterelectrode disposed in the enclosure, opposite the enclosure opening;
• a reference electrode used to regulate the current delivered by the generator
• electrical connection means arranged to be able to electrically connect at least one zone of said part and said generator;
• the generator being arranged to deliver a voltage between the counter-electrode and the electrical connection means;
• the device further comprising means for measuring the evolution over time of an intensity of current flowing between the counter-electrode and the means electrical connection.
• This device of the invention is particularly suitable for implementing any of the analysis methods according to the invention.
• this device places the speaker opening facing a conductive portion of the room.
• the surface of the part whose cleanliness and / or activation is to be evaluated is then opposite the enclosure opening and the counter-electrode.
• the electrolyte and the ions are introduced into the chamber, this electrolyte being in contact on the one hand with the counter electrode and on the other hand with the surface of the part which is at a distance from the counterelectrode.
• the generator then delivers the DC voltage current and the measurement means evaluate the evolution of the intensity of the current passing between the counter electrode and the workpiece surface.
• this measurement makes it possible to characterize the cleanliness and / or the activation of the workpiece surface.
• this device comprises means automating the analysis and automatically issuing a label (by label means information that may be in the form of an electronic instruction and / or a paper print) representative of the cleanliness and / or the activation of the measured part surface.
• label means information that may be in the form of an electronic instruction and / or a paper print
• the operator can decide the additional treatment that he must or not to subject to the part or the element that it produces.
• the measurement of the current can be done thanks to a potential chosen with respect to a known reference.
• Such a device is inexpensive to implement, usable simply by a non-specialized operator in the analysis of surface condition, usable directly in the production workshop to measure the cleanliness and / or activation of a part or element.
• FIG. 1 presents a first embodiment of a device making it possible to implement the methods according to the invention
• FIG. 1a shows a front view of a part having a surface whose cleanliness and / or activation is to be evaluated
• FIG. 1b shows a back view of the part of FIG.
• FIG. 2 shows curves of variation of the intensity measured as a function of time with a reference conductive surface, the time T being here expressed in abscissa according to the formula V (1 / T) (to facilitate the understanding of this graph the time correspondence T in seconds is also given);
• FIG. 3 shows an example of three curves of intensity evolution as a function of time measured on different parts using the method and the device of the invention (the time being here presented on the abscissa along a scale V (1 / T) and following a non-linear scale T in seconds);
• FIG. 4 is a sectional view of an embodiment of the analysis device of the invention for the quantification of a level of cleanliness and / or activation on an electrically conductive surface of a workpiece.
• the invention relates to an analysis method adapted to quantify the cleanliness and / or the activation of an electrically conductive surface of a part.
• the quantification of the cleanliness and / or the activation of a surface is important for example to condition the completion of a cleaning step or a treatment step of the surface of the part or of an element associated with the room when the analyzed surface is considered sufficiently clean.
• the conductive part is a metal alloy such as a steel alloy, an aluminum alloy, or a nickel alloy.
• this piece P can be:
• test piece used to indirectly evaluate the cleanliness and the activation of an element produced in a production line (for example the element may be a landing gear rod and the workpiece is then a specimen having undergone the same treatments as the rod , this specimen piece being preferably made of the same material as the production element).
• the area S to be analyzed of the part P is defined, which makes it possible to have a surface of fixed dimensions.
• the delimitation of the surface S makes it possible to set a parameter influencing the evolution of the current intensity I between the piece P and the counterelectrode 2.
• the surface S is delimited to be constant from one piece P to another, thus favoring the reproducibility of the measurement conditions and allowing a comparison between the measured results.
• the measured intensity evolutions using the same measurement parameters (same electrolyte, same distance D between the counterelectrode and the surface S, same ionic dosage), on two distinct parts having the same value of surface S are comparable between they. As will be seen later, if one of these parts is considered to be Pi with reference Pref, then the cleanliness / activation of the other piece P can be quantified by comparing characteristics of the measured intensity evolutions. on these parts Pref and P.
• FIGS. 1a and 1b A first way of delimiting the surface S is illustrated in FIGS. 1a and 1b where an electrically insulating layer 9 (in this case a self-adhesive plastic film) is applied to the electrode P over the entire portion of the part intended to be in contact with the electrolyte with the exception of the surface S.
• an electrically insulating layer 9 in this case a self-adhesive plastic film
• FIG. 1b we see another of the two faces of the specimen piece P. This face is entirely covered with the insulating layer 9 except for one electrical connection zone 12 intended to be remote from the electrolyte.
• an insulating strip 9 separates the electrical connection zone 12 from the surface S. The level of electrolyte is located above the surface S and at the level of the insulating strip, without touching the zone 12.
• the quantization device 0 has a level of cleanliness / activation of a surface S comprises an enclosure 4 for the introduction of the electrolyte 1.
• Means sealing member 5 extending on the periphery of an opening 6 of the enclosure 4.
• these sealing means 5 are formed by an annular flexible seal of the opening 6.
• This seal is arranged so that when is pressed on a flat surface, it provides a sealing and preferably forms an annular suction cup for maintaining the seal plated on the piece P.
• this seal has an annular groove forming a suction cup (conferring on the one hand a function of sealing between an inner zone 12 of the chamber 4 and a portion of the part and on the other hand a function of holding the chamber 4 on the part P).
• the surface S is delimited by the inner periphery of this seal (the enclosure is rigid and maintains the shape of the seal so that the defined area remains constant between two parts). Only the surface S of the part P is then vis-à-vis the opening 6 to be in contact with the electrolyte 1 contained in the chamber 4.
• sealing means 5 for any part having a piece portion of a given geometric shape, by sealing against the part portion P, there will always be the same defined surface S.
• electrical connection means 7 are used to electrically connect at least one zone of the part P and a generator G of current.
• the counter electrode 2 and the reference electrode 3 are fixed via fastening means such that the distances between the surface S and these electrodes 2, 3 remain constant during the measurement and are reproduced when replacing the piece P by another piece P having a portion of geometrically identical shape.
• the reference electrode 3 is of the calomel electrode type saturated with potassium chloride or of the Ag / AgCl type (for example with a double electrolytic chamber KCL3mol / L and a salt bridge) and the counter electrode 2 is of the platinum type. or Or.
• the electrolyte is introduced.
• the generator G of electric current I which is electrically connected to the counter electrode 2, to the reference electrode 3 and to the surface S via the electrical connection means 7 is then powered to generate a predetermined DC voltage current.
• the electrical connection means 7 comprise an electrically conductive gripper clamping an emergent portion of the piece P.
• the electrical connection means 7 comprise at least one electrical contact fixed on a conductive part of the metal part. P and away from the enclosure and the surface S which is oriented towards the inside of the enclosure.
• the seal may comprise electrically conductive portions placed outside the chamber, away from the electrolyte, to allow electrically connecting the surface S to the generator G without these connecting means 7 do not come into contact with the electrolyte 1.
• Generator G delivers a constant voltage V between the counter-electrode 2 and the electrical connection means 7, which makes it possible to have a constant voltage V between the surface S and the counter-electrode 2.
• This voltage V applied between the counter-electrode 2 and the means of electrical connection 7 connected to the surface S is evaluated / regulated by measurement with the aid of the reference electrode 3.
• the intensity I of the current between the counter electrode 2 and the surface S is measured with the help of an ammeter belonging to measuring means M of the evolution in time of an intensity I.
• the generator G and the measuring means M may belong to a potentiostat connected to the electrodes 2, 3 and the means 7, this potentiostat recording the results of the measurement of I. It is also noted that for the proper functioning of the device, cathodic resistance can be obtained by using a cathode cable having a predetermined resistance.
• the voltage V (that is to say the voltage between the surface S and the counter-electrode 2) also remains constant during the measurement of evolution in the time of the intensity I.
• the voltage regulation is such that the absolute value of these constant voltages V or V remains less than or equal to a predetermined voltage threshold.
• the voltage threshold is less than 0.5 volts, preferably less than 0.2 volts and preferentially less than or equal to 0.15 volts and greater than 0.05 volts.
• the constant voltage V is chosen to be equal to the threshold of 0.15 volts, which makes it possible to avoid degrading the surface S during the analysis since the voltage V which is less than or equal to V will not exceed 0.15 volts.
• the device of the invention carries out a three-electrode voltammetric type measurement making it possible to characterize the evolution of the electrochemical reaction in an electrolyte 1.
• the constant voltage V applied between the counterelectrode 2 and the surface S it is measured a voltage representative of the voltage between the reference electrode 3 and the surface S.
• the measurement of the intensity I makes it possible to quantify the flow of charges at the surface S while the voltage V and the voltage V remain constant .
• n number of electrons exchanged by the system
• the parameter K, Kn is representative of the rate of variation of the intensity I measured over the measuring time range X.
• the comparison between Kn and Kref is performed by calculating the Kn / Kref ratio (in%).
• Kn is the slope of the linear regression line of the variation of intensity I measured over a time range X with the part Pn to be tested and subjected to the constant potential V.
• KRef is the slope of the linear regression line of the intensity variation I measured over a time range X with the reference part PRef and subjected to the constant potential V.
• the range X begins after supplying current to the counter electrode for a predetermined time preferably greater than 5 seconds and preferably between 10 and 20 seconds.
• the intensity I evolution curve is more representative of the cleanliness / activation of surface S on the X range than it is on the Y range (the Y range extends from the beginning the power supply of the counter-electrode and the start of the X range) ⁇
• FIG. 3 represents, on the range X, the curves C1, C2, Cref of respective evolutions of intensities I for different pieces PI, P2, P Ref .
• Curve C2 corresponds to the variation of intensity I measured with a greased piece P2 and having spent a few seconds in a degreasing bath.
• the curve Ci corresponds to the intensity variation I measured with a PI piece having undergone a cleaning / degreasing treatment greater than that of the piece P2.
• the curve Cref corresponds to the variation of intensity I measured with the reference part Pref which is perfectly degreased (Pref was prepared by immersion in a degreasing bath for at least six times longer than the immersion time of the PI piece, then Pref was prepared by a surface finish with acetone applied with a wipe, followed by a double degreasing treatment and a new finish with acetone followed by sanding and a mirror polishing finish).
• the range Y does not appear because it is considered irrelevant for estimating the preparation of the surface S, and only the range X is represented.
• the time origin of the measurement has been shifted to coincide with the beginning of the relevant range X.
• the electrolyte 1 is the same for each of the measurements.
• This electrolyte 1 comprises:
• salts chosen from halogenated salts, ammonium salts, carbonate salts, organic salts such as carboxylates, cyanide salts, organomagnesium salts; and
• a polar solvent which may be more or less viscous, for example ketones, alcohols, aldehydes, aqueous media, gels;
• the acid is selected from the group of acids comprising inorganic acids such as othophosphoric acid, sulfuric acid and an organic acid such as carboxylic acid.
• the base is selected from the basic group consisting of soda, potash and ammonia.
• This electrolyte 1 may have the form of a liquid or a gel, the gel having the advantage of being easier to apply to the surface of the part because it flows less than the liquid.
• the gel may be a gel based on silica and / or Agar Agar.
• the electrolyte comprises:
• Fe2 + and Fe3 + ions of Ferrocyanide and Ferricyanide form an electrochemical couple favorable to the observation of the Cotterell's law without undesirable deposition on the analyzed surface S.
• the Fe2 + / Fe3 + couple makes it possible to work on V potentials very low where the phenomenon of oxygen reduction does not exist. It is therefore not mandatory to inert the enclosure with nitrogen to avoid the risk of explosion.
• Ferrocyanide and Ferricyanide Another advantage of Ferrocyanide and Ferricyanide is that cyanide stabilizes the system (Fe2 + ions normally have instability over time).
• the working pressure pressure of the electrolyte
• the type of atmosphere surrounding the electrolyte in the chamber can be chosen according to the level of precision of the desired measurement.
• the pressure may be atmospheric, under vacuum or at a pressure greater than atmospheric pressure.
• the type of atmosphere used may be air or its derivatives (air enriched with oxygen, pure O 2, N 2, CO 2) or one or more insoluble organic gases in the medium used (the pollutions generate fluctuations in electrochemical resistance). distorting the measurements or making it difficult to read the results);
• a grounded faraday cage can be placed around all or part of the enclosure 4, the part P and / or the generator G.
• the device of the invention 0 also comprises a pump 10 hydraulically connected to an electrolyte reservoir 11 and to the internal zone Z of the enclosure 4.
• This pump 10 is controlled by means of control means Cde to selectively fill or empty the chamber of one electrolyte.
• control means Cde order the filling of the chamber 4 in electrolyte 1 to plunge the electrodes 2 , 3 and the surface S. Then the control means Cde:
• the measuring means M so that they evaluate the evolution of the intensity I in the time T.
• the means Cde controls the emptying of the chamber 4 by the pump 10 towards the tank 11.
• the temperature of the catalyst 1 is preferably regulated, by means of thermal regulation of the device, to be within a predetermined range of temperature values (15 ° C). 30 ° C).
• the electrodes 2, 3 are immobilized at least throughout the duration of the intensity measurement.
• the element for which the cleanliness / activation is evaluated is a landing gear pin
• this evaluation is done by positioning several pieces / test pieces at predetermined key locations around the rod during its surface preparation phase. Then these pieces / specimens which have a whole conductive surface are analyzed with the method of the invention, and one thus deduces the state of surface preparation of the rod at different locations of rod.
• the method of the invention can be used to produce a map of the cleanliness and / or activation of the rod.
• the invention by measuring the cleanliness / activation of a part, can be used to characterize the quality of the part preparation process (for example to highlight areas of treatment defect, or to follow the aging of degreasing bath or possibly to qualify a detergent).

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• 2012
  • 2012-05-14 FR FR1254380A patent/FR2990513B1/fr active Active
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