WO2022189727A1

WO2022189727A1 - Element for detecting the corrosion or the possibility of corrosion of a part

Info

Publication number: WO2022189727A1
Application number: PCT/FR2022/050360
Authority: WO
Inventors: Ioannis STASINOPOULOS; Maya GEAGEA; Oscar D'almeida; Minh Chau Phan Huy; Loic EXBRAYAT; Nassim SALHI; Jacques ECHOUARD; Gérald LOPEZ
Original assignee: Safran
Priority date: 2021-03-12
Filing date: 2022-03-01
Publication date: 2022-09-15

Abstract

The invention relates to an element (1) for detecting the corrosion or the possibility of corrosion of a part, comprising particles (10) encapsulating a modifying agent (12) which is capable of being released in the presence of a compound associated with the corrosion of the part so as to chemically eliminate at least one portion of the detection element (1) and thus modify the propagation of the physical signal (SO) in this element.

Description

Title of the invention: ELEMENT FOR DETECTION OF CORROSION OR THE POSSIBILITY OF CORROSION OF A PART

Technical area

An element for detecting corrosion or the possibility of corrosion of a part which is able to undergo an alteration in the presence of a compound associated with the corrosion of said part. This alteration produces a modification in the propagation of the physical signal in the detection element, the highlighting of which is used to obtain information on the state of corrosion or the possibility of corrosion of the part. The invention also relates to an assembly including the detection element, the part to be checked and a control unit capable of detecting the modification of the propagation of the physical signal, as well as an associated method.

Prior technique

Various methods have been described in the state of the art for detecting the corrosion of a part, in particular in the aeronautical or aerospace field.

In this regard, mention may be made of application WO 2018/193220 which discloses a coating containing nanocapsules capable of producing a fluorescence signal in the presence of a corrosion product of a part, in this case a metal ion.

It nevertheless remains desirable to propose new devices and method for detecting the corrosion of a part, or the simple possibility of corrosion of a part.

Disclosure of Invention

According to a first embodiment, the invention relates to an element for detecting corrosion or the possibility of corrosion of a part, the detection element comprising a conduction portion capable of transmitting a physical signal, the detection being characterized in that it incorporates particles encapsulating a modifying agent which is capable of being released in the presence of a compound associated with the corrosion of the part, said modifying agent being capable, when it is released, of chemically eliminating at least part of the detection element so as to modify the propagation of the physical signal in the conduction portion.

The invention is based on detecting corrosion or the possibility of corrosion of the part by altering the structure of the detection element produced following the release of the modifying agent which is triggered by contact with the compound associated with the corrosion of the part. This alteration leads to a modification of the propagation of the physical signal in the detection element, which is highlighted in order to obtain information on the state of corrosion or on possible corrosion of the part in the future.

Various embodiments are possible and will be detailed below.

The physical signal can be an optical or electrical signal, for example.

The compound associated with the corrosion of the part can be a product resulting from the corrosion of the part, such as an H ⁺ ion, a hydroxide ion (OH ), or an entity comprising a metal from the part, such as an ion of a part metal. In this case, the detection element makes it possible to identify corrosion of the part which has already occurred. As a variant or in combination, the compound associated with the corrosion of the part can be an entity capable of corroding the part and/or of catalyzing this corrosion, such as an H ⁺ ion or a halide ion, such as a chloride or fluoride ion. . In this case, the detection element makes it possible to identify possible corrosion of the part, which has not necessarily yet occurred. It is thus possible to detect corrosion from the very beginning in order to take appropriate measures to avoid it or reduce its consequences.

The modification of the propagation of the physical signal following the release of the modifying agent can be a reduction in the transmission capacity of the physical signal in the conduction portion, for example a total or almost total loss of this transmission capacity. As a variant or in combination, the modification of the propagation of the physical signal following the release of the modifying agent can comprise at least one of a frequency shift of the physical signal, a phase shift of this signal or a change in the shape of this physical signal. In an exemplary embodiment, the modifying agent is capable, when it is released, of dissolving said at least part of the detection element.

According to this example, the modifying agent is a solvent for all or part of the detection element. This choice constitutes a relatively simple solution to allow the elimination of said at least part of the detection element.

As a variant or in combination, the modifying agent is able, when it is released, to consume said at least part of the detection element by chemical reaction.

In an exemplary embodiment, the particles are present in said at least part of the detection element and the sum of the external surfaces of said particles relative to the volume of said at least part being between 60 m ¹ and 6.10 ⁸ m ¹ .

Such a characteristic advantageously implements a sufficiently high quantity of particles to produce a substantial modification of the propagation of the physical signal in the presence of the compound associated with the corrosion of the part, while limiting the quantity of these particles in order to avoid any risk alter the properties of the sensing element in normal operation (without corrosion or possibility of corrosion).

In an exemplary embodiment, the particles comprise a wall encapsulating the modifying agent, said wall comprising a first internal layer insensitive to the modifying agent and able to open in the presence of the compound associated with the corrosion of the part to release the modifying agent, and a second outer layer adapted to open on contact with the modifying agent.

Such a characteristic advantageously makes it possible to have a particularly sensitive detection element, making it possible, after the release of the modifying agent outside of one particle, to cause a cascade release of the modifying agent outside the others. particles, and thus produce a very significant modification of the propagation of the physical signal in the conduction portion.

In an exemplary embodiment, the detection element is an optical waveguide. In particular, the detection element can be an optical fiber. More particularly, the optical fiber may comprise at least one core forming a conduction portion capable of transmitting an optical signal, and a sheath surrounding the core, and the particles may be present in at least one of the core and of the sheath.

Alternatively, the sensing element is an electrical conductor. The detection element can thus be in the form of one or more conductive wires or tracks possibly present within a sheath, for example.

The invention also relates, according to this first embodiment, to an assembly for detecting corrosion or the possibility of corrosion of a part, comprising at least:

- a detection element as described above,

- a part in contact with the detection element, and

- a control unit capable of detecting the modification of the propagation of the physical signal in the conduction portion following the chemical elimination of said at least part of the detection element by the modifying agent.

In an exemplary embodiment, the part is an aircraft part, for example a landing gear.

The invention also relates, according to this first embodiment, to a method for detecting corrosion or the possibility of corrosion of a part implementing an assembly as described above, comprising at least:

- the detection of a possible modification of the propagation of the physical signal in the conduction portion using the control unit, and

- the determination of a state of corrosion or possible corrosion of the part from the detection carried out.

According to a second embodiment, the invention relates to an assembly for detecting corrosion or the possibility of corrosion of a part, comprising at least:

- a detection element comprising a conduction portion capable of transmitting a physical signal, and

- a part in contact with the detection element, said part incorporating particles encapsulating a modifying agent which is capable of being released in the presence of a compound associated with the corrosion of the part, said modifying agent being capable, upon its release, of chemically eliminating at least part of the so as to modify the propagation of the physical signal in the conduction portion.

As for the first embodiment, the invention is based on detecting corrosion or the possibility of corrosion of the part by altering the structure of the detection element produced following the release of the modifying agent which is triggered by contact with the compound associated with the corrosion of the part. This alteration leads to a modification of the propagation of the physical signal in the detection element, which is highlighted in order to obtain information on the state of corrosion or on possible corrosion of the part in the future.

Various embodiments are possible and will be detailed below. As for the first embodiment, the physical signal can be an optical or electrical signal, for example.

As with the first embodiment, the compound associated with the corrosion of the part can be a product resulting from the corrosion of the part, such as an H ⁺ ion, a hydroxide ion (OH ) or a species comprising a metal originating from the piece, like an ion of a piece metal. In this case, the detection element makes it possible to identify corrosion of the part which has already occurred. As a variant or in combination, the compound associated with the corrosion of the part can be an entity capable of corroding the part and/or of catalyzing this corrosion, such as an H ⁺ ion or a halide ion, such as a chloride or fluoride ion. . In this case, the detection element makes it possible to identify possible corrosion of the part, which has not necessarily yet occurred. It is thus possible to detect corrosion from the very beginning in order to take appropriate measures to avoid it or reduce its consequences.

As for the first embodiment, the modification of the propagation of the physical signal following the release of the modifying agent can be a reduction in the transmission capacity of the physical signal in the conduction portion, for example a total or near total loss. total of this transmission capacity. In Alternatively or in combination, the modification of the propagation of the physical signal following the release of the modifying agent can comprise at least one of a frequency shift of the physical signal, a phase shift of this signal or a modification of the shape of this physical signal.

In an exemplary embodiment, the modifying agent is capable, when it is released, of dissolving said at least part of the detection element.

In an exemplary embodiment, the particles are present in at least one zone of the part and the sum of the external surfaces of said particles relative to the volume of said at least one zone being between 60 m ¹ and 6.10 ⁸ m ¹ .

Such a feature advantageously makes it possible to have a particularly sensitive detection assembly, allowing after the release of the modifying agent outside of one particle to cause a cascade release of the modifying agent outside the others. particles, and thus produce a very significant modification of the propagation of the physical signal in the conduction portion.

In an exemplary embodiment, the detection element is an optical waveguide. In particular, the detection element can be an optical fiber.

In an exemplary embodiment, the part comprises a substrate coated with at least one layer in which the particles are present, the detection element being in contact with said at least one layer.

In particular, the layer can be an anti-corrosion layer.

Alternatively or in combination, the layer may be a layer of paint.

In an exemplary embodiment, the assembly further comprises a control unit capable of detecting the modification of the propagation of the physical signal in the conduction portion following the chemical elimination of said at least part of the detection element by the modifying agent.

The invention also relates, according to this second embodiment, to a method for detecting corrosion or the possibility of corrosion of a part implementing an assembly as described above, comprising at least:

Brief description of the drawings

[Fig. 1] FIG. 1 represents, schematically and in cross section, an example of a detection element according to the first embodiment of the invention in the form of an optical fiber, before release of the modifying agent. [Fig. 2] FIG. 2 represents, schematically and in cross section, the optical fiber of FIG. 1 in the presence of a compound associated with the corrosion of the part.

[Fig. 3] FIG. 3 represents, schematically and in cross section, the chemical elimination of part of the cladding of the optical fiber of FIG. 1 following the release of the modifying agent.

[Fig. 4] FIG. 4 represents, schematically and in cross section, the evolution of FIG. 3 with the elimination of an additional part of the sheath of the optical fiber.

[Fig. 5] Figure 5 shows, schematically and in cross section, a variant of the situation illustrated in Figure 4 with the additional elimination of part of the heart of the optical fiber.

[Fig. 6] FIG. 6 schematically represents an example of an assembly according to the first embodiment of the invention incorporating a detection element according to the invention in the form of an optical fiber.

[Fig. 7] FIG. 7 schematically represents another example of an assembly according to the first embodiment of the invention incorporating a detection element according to the invention in the form of an optical fiber.

[Fig. 8] Figure 8 schematically shows another example of an assembly according to the first embodiment of the invention incorporating a detection element according to the invention in the form of an optical fiber.

[Fig. 9] FIG. 9 schematically represents a variant of a detection element according to the first embodiment of the invention in the form of an electrical conductor, before release of the modifying agent.

[Fig. 10] Figure 10 schematically shows the detection element of Figure 9 after release of the modifying agent.

[Fig. 11] FIG. 11 schematically represents a variant of particles encapsulating the modifying agent which can be implemented within the scope of the invention.

[Fig. 12] Figure 12 schematically represents the diffusion of the compound associated with the corrosion of the part within the particle of figure 11. [Fig. 13] Figure 13 schematically shows the opening of the inner layer of the wall of the particle of Figure 11 and the release of the modifying agent.

[Fig. 14] Figure 14 schematically shows the cascade release of the modifying agent following its release.

[Fig. 15] FIG. 15 schematically represents an example of an assembly according to the second embodiment of the invention incorporating a detection element in the form of an optical fiber.

[Fig. 16] Figure 16 schematically shows the presence of particles in an anti-corrosion layer of the part of the assembly of Figure 15.

[Fig. 17] FIG. 17 represents, schematically and in cross section, an example of a detection element that can be implemented within the framework of the second embodiment of the invention in the form of an optical fiber, before release of the modifying agent.

[Fig. 18] FIG. 18 schematically represents the release of the modifying agent following contact with a compound associated with the corrosion of the part.

[Fig. 19] Figure 19 shows, schematically and in cross section, the chemical removal of part of the cladding of the optical fiber of Figure 17 following the release of the modifying agent.

[Fig. 20] Figure 20 represents, schematically and in cross section, the evolution of Figure 19 with the elimination of an additional part of the sheath of the optical fiber.

[Fig. 21] FIG. 21 represents, schematically and in cross-section, a variant of the situation illustrated in FIG. 20 with the additional elimination of part of the core of the optical fiber.

[Fig. 22] FIG. 22 schematically represents another example of an assembly according to the second embodiment of the invention incorporating a detection element in the form of an optical fiber.

[Fig. 23] Figure 23 schematically shows another example of an assembly according to the invention incorporating a detection element in the form of an optical fiber. [Fig. 24] FIG. 24 schematically represents a variant of a detection element that can be implemented in the context of the second embodiment of the invention after release of the modifying agent.

Description of embodiments

Figure 1 illustrates an example of detection element 1 according to the first embodiment of the invention, useful for detecting corrosion or the possibility of corrosion of a part. In the example illustrated, the detection element 1 is an optical fiber which is illustrated, in FIG. 1 as well as in FIGS. 2 to 5 which will be described subsequently, in cross section with respect to its longitudinal axis.

The optical fiber 1 comprises a core 3 forming a conduction portion which is capable of transmitting an optical signal along the longitudinal axis of the fiber 1. The possible directions for the propagation of the optical signal SO are illustrated in FIG. forward relative to the drawing plane or backward relative to this plane). The core 3 can comprise silica or a polymeric material, such as poly(methyl methacrylate) (PM MA) or polystyrene (PS). The optical fiber 1 further comprises a sheath 5 which surrounds the core 3 and participates in the confinement of the optical signal in the core 3. The sheath 5 can be in contact with the heart 3. The sheath 5 can comprise silica or a polymeric material, such as poly(methyl methacrylate) (PMMA) or polystyrene (PS). Optionally, the optical fiber 1 may comprise one or more additional coatings surrounding the sheath 5 and the core 3. The coating or coatings may be made of polymeric material, such as a polyacrylic, a silicone, a polyimide, a polyetheretherketone (PEEK), poly(butylene terephthalate) (PBT), polypropylene (PP), polyethylene (PE), poly(vinyl chloride) (PVC), polyurethane (PU), fluoropolymer, such as ethylene tetrafluoroethylene (ETFE ), a polytetrafluoroethylene (PTFE), be made of carbon, or of a metallic material. In the example illustrated in Figures 1 to 5, the optical fiber 1 is devoid of such a coating and only comprises the core 3 and the sheath 5. The following examples in connection with Figures 6 to 8 which will be described below show, for their part, the presence of a metal coating 7 surrounding the optical fiber. In a way In general, the optical fiber 1 can be doped or undoped, monomode or multimode, or optionally with a refractive index gradient.

The optical fiber 1 comprises particles 10 encapsulating a modifying agent 12 which makes it possible to chemically eliminate in contact with it at least a part of the detection element 1. These particles 10 are housed within the optical fiber 1. In the illustrated example, the particles 10 are present in the sheath 5 but it is not beyond the scope of the invention if these particles are also present in the core 3, or are only present in the core 3. The particles 10 can be of the size any, for example micrometric, having for example a D50 size comprised between 10 μm and 100 μm, or nanometric, having for example a D50 size comprised between 10 nm and 999 nm. In a manner known per se, the average size D50 designates the dimension given by the statistical particle size distribution to half of the population. It is, of course, not departing from the scope of the invention if a mixture of micrometric and nanometric particles 10 is used, or more generally mixtures of particles 10 of different size D50, or else of different composition. As such, it is possible to use first particles encapsulating a first modifying agent and second particles encapsulating a second modifying agent different from the first modifying agent. Each of the first and second modifying agents being able to eliminate a distinct part of the detection element, for example the first modifying agent is able to eliminate the sheath 5 of the optical fiber and the second modifying agent is able to eliminate the core 3 optical fiber which is made of a material different from that of the sheath 5. On the same principle, it is also possible to use particles 10 which encapsulate the mixture of the first and second modifying agents which have just been described.

The particles 10 can be in the form of capsules or “core-shell” particles comprising a wall 14 surrounding and containing the modifying agent 12. The particles 10 can only comprise the modifying agent 12 which allows to chemically eliminate at least part of the detection element 1 and a wall 14 encapsulating this modifying agent 12. The particles 10 can thus be devoid of third-party compound other than the modifying agent 12 and the wall 14 of these particles encapsulating this agent 12. In particular, the particles 10 can only comprise the wall 14 and the modifying agent 12 constituting a solvent for at least part of the detection element 1. As a variant, the particles 10 can comprise an auxiliary compound distinct from the agent modifier 12 and not reactive with it. The thickness of the wall 14 of the particles 10 can be greater than or equal to 1 nm, for example between 1 nm and 5 μm, for example between 1 nm and 1 μm. The wall 14 can be single-layer or optionally multi-layer, as will be described below. The particles 10 can be of substantially spherical shape or of elongated shape, for example in the form of fibers. The particles 10 may be present in said at least part of the detection element and the sum of the outer surfaces of the particles 10 per unit volume of said part may be between 60 m ¹ and 6.10 ⁸ m ¹ . The particles 10 can be present over at least half the thickness of the sheath 5 and/or of the core 3, or even over substantially the whole of this thickness. The particles 10 can be uniformly dispersed in the volume of said at least part of the detection element 1, for example be uniformly dispersed in the sheath 5 and/or the core 3. However, this does not depart from the scope of the invention if the distribution of the particles 10 is not uniform. It is for example possible to have a first concentration by volume of particles 10 in a first radial part of the sheath 5 located on the side of the heart which is greater than a second concentration by volume of particles (possibly zero) in a second radial part of the sheath 5 located on the side opposite the heart 3. Such an example is advantageous because it makes it possible to guarantee a significant modification of the physical signal in the conduction portion during the release of the modifying agent, thus increasing the detection sensitivity. In general, the presence of particles 10 in the optical fiber 1 is determined so as to obtain a detectable modification of the propagation of the optical signal, following the release of the modifying agent 12. The choice of the diameters of the core and of the cladding, in combination with the wavelength chosen, will determine the distribution of the optical power between the core of the cladding. Relatively thin sheaths can be favored so as to ensure that the zone in which the particles 10 release the modifying agent 12 has a dimension comparable to the extent of the optical mode in the cladding 5, in order to be able to easily detect the modification of the propagation of the optical signal without having to alter the core 3. The core 3 can nevertheless be altered if a strong modification of the propagation of the signal optics is sought, in order to facilitate detection. In general, the person skilled in the art knows how to determine, using his general knowledge, the dimensions of the core 3 and of the sheath 5 to be adopted as well as the distribution of the particles 10 in the optical fiber, so as to obtain a modification detectable optical signal propagation.

As indicated above, the modifying agent 12 is able to be released in the presence of a compound associated with the corrosion of the part, which can be a product resulting from the corrosion of the part or an entity able to corrode the part and /or to catalyze this corrosion. This release leads to a chemical elimination of at least part of the detection element 1 leading to an alteration of the propagation of the physical signal in the conduction portion 3. The following illustrates, in connection with FIGS. 2 to 5, the chemical elimination of at least part of the optical fiber 1 following the release of the modifying agent 12.

FIG. 2 illustrates the optical fiber of FIG. 1 in the presence of the compound 16 associated with the corrosion of the part, for example an H ⁺ ion or an OH ion or even a halide ion, which allows the release of the modifying agent 12 The compound 16 diffuses into the detection element 1, in particular into the sheath 5 and possibly the core 3 of the optical fiber 1. FIG. with compound 16. This release produces a chemical elimination of the sheath 5 of the optical fiber 1 by a dissolution or chemical reaction mechanism, as will be described in more detail below. The release of the modifying agent 12 can be due to a total or partial destruction of the wall 14 in contact with the compound 16. partial or total of this wall and the release of the encapsulated modifying agent 12. FIG. 4 shows the evolution over time of the chemical elimination of the optical fiber 1 as it is brought into contact with the compound 16. This bringing into contact results in a greater elimination of the sheath 5 than that illustrated in FIG. 3 so that the effect of modification of the optical signal is maximized without however disturbing the heart 3 which is here another material, insensitive to the modifying agent 12. FIG. 5 illustrates a variant of FIG. 4 in which there is, in addition to the total or partial elimination of the sheath 5, a total or partial elimination of the core 3 The alteration of the optical fiber 1 produced following the bringing into contact with the compound 16 can lead to a rupture of the optical fiber 1, or simply to a damage of the latter, which can be demonstrated by detecting a change in the propagation of the optical signal compared to the situation before the release of the modifying agent.

We have just described, in connection with FIGS. 1 to 5, the general structure of an example of optical fiber 1 according to the invention as well as the evolution of the alteration of this fiber 1 produced following the release of modifying agent 12. The following describes various examples of materials that can be used to form the particles 10.

The wall 14 of the particles 10 can be formed from various materials, organic or inorganic. By way of example, the wall 14 can be made of silica, a polymeric material, such as a polyurea, a urea-formaldehyde or melamine-formaldehyde resin, or a polysaccharide, such as chitosan or an alginate optionally forming a complex with a metal ion, such as a silver ion.

As indicated above, the modifying agent 12 can be a solvent for at least part of the detection element 1. The release of the modifying agent 12 makes it possible in this case to dissolve all or part of the detection element. detection 1. The modifying agent 12 can be an organic solvent, an acid or a base. When the modifying agent 12 is an organic solvent, it can comprise at least one of the following compounds: ethyl acetate, benzene or benzene derivative such as toluene, o-xylene, chlorobenzene, acetone, tetrahydrofuran (THF ), trichlorethylene, dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dichloromethane, dichloroethane, cyclohexane, chloroform, anisole, styrenes. The modifying agents 12 listed above can in particular be useful for dissolving poly(methyl methacrylate) or polystyrene, for example. When the modifying agent 12 is an acid, it can comprise at least one of the following compounds: hydrofluoric acid (HF), hydrochloric acid (HCl), sulfuric acid (H ₂ S0 ₄ ) or acetic acid. When the modifying agent 12 is a base, it can comprise sodium hydroxide (NaOH). The acid modifying agents listed above may in particular be useful for dissolving silica, and sodium hydroxide may in particular be useful for dissolving polymeric materials or silica.

As a variant or in combination, the release of the modifying agent 12 can consume all or part of the detection element by chemical reaction. In this case, the modifying agent 12 can for example comprise sodium hydroxide. The use of sodium hydroxide as a modifying agent 12 can make it possible to consume said at least part of the detection element formed from a polymeric material, for example polyester, by chemical reaction.

The manufacture of particles 10 is carried out by implementing techniques known per se. The modifying agent 12 to be encapsulated is determined according to the nature of the material of the detection element to be chemically eliminated. A wall material 14 of compatible particles is then chosen, for example which is not substantially eliminated by the modifying agent itself in order to avoid an undesired release, but capable of allowing the release in the presence of the associated compound 16 corrosion of the part. It will be noted that the invention is not limited to the use of walls of particles insensitive to the modifying agent as will be detailed below in connection with FIGS. 11 to 14.

As examples of publications describing techniques for encapsulating an agent in particles, mention may be made of the publication Zhao et a!

“Microencapsulation of Hydrophobia Liquids in Closed All-Silica Colloidosomes” (Langmuir, 2014, 30, 4253) which describes in particular the encapsulation of toluene in silica particles. The publication Sousa et a! “Chitosan Microspheres as Carriers for pH—Indicating Species in Corrosion Sensing” (“Macromolecular Materials and Engineering, Volume 305, Issue 2”) describes the encapsulation of acetic acid in chitosan microcapsules. The Esser-Kahn et a! "Triggered Release from Polymer Capsules" (Macromolecules 2011, 44, 14, 5539-5553) describes different encapsulation methods. The publication Maia et a! "Active sensing coating for early detection of corrosion processes"("RSC Adv., 2014, 4, 17780-17786") describes, for its part, the encapsulation of an agent comprising acetone in particles with a polyurea. The publication Xiong et a! "A novel capsule-based self-recovery System with a chloride ion trigger" proposes the use of particles having a wall formed by a complex of a silver ion and a polysaccharide capable of releasing the encapsulated compound on contact with a halide ion (DOI: 10.1038/srepl0866). Different encapsulation methods known per se can be implemented such as emulsification, for example with an “oil in water” emulsion, or drying by atomization (“spray drying”).

The description below describes examples of combinations of materials that can be implemented within the scope of the invention.

According to an example when the modifying agent 12 is an organic solvent, the wall 14 can be made of inorganic material, for example silica, or of polymeric material, for example urea-formaldehyde, melamine-formaldehyde, polyurea or optionally complexed polysaccharide. by a metal ion, said at least part of the detection element 1 intended to be chemically eliminated can be made of polymeric material, such as poly(methyl methacrylate) or polystyrene, and the compound associated with the corrosion of the part allowing the release of the modifying agent can be an H ⁺ ion, an OH ion, or a halide ion. Preferably, the organic solvent modifying agent may be acetone.

According to another example when the modifying agent 12 is an acid, the wall of the particles 10 can be made of polymeric material, for example of polysaccharide, for example of chitosan, said at least part of the detection element intended to be eliminated chemically may be silica, and the compound associated with the corrosion of the part allowing the release of the modifying agent may be the OH ion. In the case of an optical fiber forming the detection element 1, the optical fiber can be manufactured by a fiber manufacturing process using a modified chemical vapor deposition technique (“Modified Chemical Vapor Deposition Fiber Fabrication Method”; “ MCVD"), or by an assembly-drawing technique ("stack-and-draw technique") or even by extrusion which are known per se, in which there is added in the core 3 and/or the sheath 5 the particles 10 described above. It is also possible to use sol-gel techniques to form the optical fiber, which are known per se.

The description that has just been given has provided structural and manufacturing details relating to a detection element 1 in the form of an optical fiber. The following sets out to describe, in connection with FIGS. 6 to 8, various possible arrangements for instrumenting a part to be inspected by this type of element.

FIG. 6 illustrates an example of an assembly 20 according to the first embodiment of the invention implementing a detection element 1 in the form of an optical fiber of the type described above. This assembly 20 comprises a part 22 whose corrosion or the possibility of corrosion is to be assessed. This part 22 is in contact with the detection element 1. A single detection element 1 has been shown in contact with the part 22 but this does not depart from the scope of the invention when the part 22 is provided with a plurality of detection elements 1 in contact with it. The part 22 may, as shown, be in the form of a substrate 24 coated with one or more layers 26, 28 of coating. In the examples illustrated in Figures 6 to 8, the layer or layers 26 are anti-corrosion layers, and the layer 28 is a paint layer, optionally comprising an anti-corrosion ^primer and a polyurethane finish, or simply a primer with nti-corrosion. According to a variant not shown, the part can be in the form of an uncoated substrate. Whatever the embodiment considered, the substrate 24 can be metallic, for example steel, aluminum or aluminum alloy. In the case where the substrate 24 is made of steel, the anti-corrosion layer or layers 26 can be made of ZnNi, ZnFe, or be layers obtained by cadmium plating. In case the substrate 24 is made of aluminum or an aluminum alloy, the anti-corrosion layer(s) 26 may be anodization layers.

In each of the examples illustrated in Figures 6 to 8, the detection element 1 is in contact with at least one of the coating layers of the part 22, and in particular in contact with at least one anti-corrosion layer 26. It may be advantageous, as shown, for the optical fiber 1 to be coated on its outer surface with a metal coating 7 (covering the sheath 5) in order to promote the adhesion of the fiber to an anti-corrosion layer 26 of the room. This coating 7 can for example be made of zinc, nickel, aluminum, titanium, magnesium, niobium, zirconium, hafnium, tantalum, or one of their alloys, or a ZnNi coating.

According to a first example of assembly 20 illustrated in FIG. 6, the optical fiber 1 is inserted between the anti-corrosion layer 26 and the paint layer 28. In this case, the optical fiber 1 can be in contact with the anti-corrosion layer -corrosion 26 and the paint layer 28. According to a second example of assembly 20a illustrated in Figure 7, the optical fiber 1 is inserted between the substrate 24 and the anti ^¬ corrosion layer 26. In this case, the optical fiber 1 may be in contact with the anti- ^corrosion layer 26 and the substrate 24. According to a third example of an assembly 20b illustrated in FIG. 8, the optical fiber 1 is inserted between two anti-corrosion layers 26, and may be in contact of these two layers 26. The configurations of the first and third examples (FIGS. 6 and 8) make it possible to detect corrosion before attack on the substrate 24.

When it is corroded, the anti-corrosion layer 26 can form hydroxides, for example zinc hydroxides, which cause the release of the encapsulated modifying agent, and the degradation of the optical fiber 1 as described above. As a variant, the anti-corrosion layer 26 can be inert and the detection element 1 can simply detect an entity able to corrode the part and/or to catalyze this corrosion, such as an H ⁺ ion. One can advantageously choose a modifying agent 12 which attacks exclusively the material of the optical fiber 1, and in particular not the part 22, that is to say neither the substrate 24, nor a coating layer 26 or 28. The assembly 20 further comprises a control unit 30 or “interrogator” (represented only in FIG. 6) which is capable of detecting the modification of the propagation of the physical signal in the conduction portion following the chemical elimination of said at least a part of the detection element 1 by the modifying agent 12. The control unit 30 can be fixed, for example mounted on an aircraft comprising the part 22 to be inspected, which can make it possible to carry out the detection in continuously, and in particular during the operating phases of the part 22. As a variant, the control unit 30 can be connected to the detection element 1 only to carry out the control, then disconnected once the control has been carried out (control unit 30 removable). The signal coming from the control unit can be transmitted and analyzed by a computer which can return a result giving information on the state of corrosion or the possibility of corrosion of part 22.

The control unit can implement an opto-electronic system. The techniques for detecting a modification of the propagation of a physical signal in a portion of conduction following an alteration of a conductor are known per se. In the case of a detection element in the form of an optical fiber 1, it is possible to implement a control technique by reflectometry, for example using an optical time domain reflectometer (“Optical Time Domain Reflectometer”; “OTDR”) or an optical frequency domain reflectometer (“Optical Frequency Domain Reflectometer”; “OFDR”). The use of an “OTDR” reflectometer can be favored in the case of significant degradation of the detection element 1 following the release of the modifying agent 12. The use of an “OFDR” reflectometer can be suitable for small degradations of the detection element 1, and has improved performance in terms of spatial resolution compared to the “OTDR” technique. These methods also have the advantage of being able to detect the damage over the entire length of the detection element, and not only at certain predefined positions, as well as to locate the location of the damage. The control unit 30 can allow control by Rayleigh scattering so as to identify a loss or attenuation of the signal following the alteration of the detection element 1 caused by the release of the modifying agent 12. Rayleigh scattering can enable a slight removal of the sensing element to be detected. Alternatively, the unit of control 30 can allow pumping through the sheath 5 in which a beam is injected through the sheath 5 so as to increase the power of the light signal propagating in the heart 3, and thus detect any modification of this signal following the alteration fiber optic. Indeed, a chemical alteration at the level of the cladding 5 leads to a change in coupling between the main wave in the core 3 and the wave injected by the cladding 5. This leads to a modification of the optical power, which is easily detectable. It is also possible to use one or more Bragg gratings in the optical fiber 1, and to detect the modification of propagation of the optical signal by analysis of the spectral response in transmission or in reflection. The Bragg grating or gratings will be able to detect the damage if the latter has occurred nearby, and in this case make it possible to trace the location of the damage. A sheath 5 partially eliminated following the release of the modifying agent 12 could lead to a modification of the spectral response of the Bragg grating. A total elimination of the sheath 5 could lead to a complete or substantially complete loss of the optical signal.

The description which has just been given, in connection with FIGS. 1 to 8, has detailed the case of a detection element in the form of an optical fiber 1 for which a conclusion as to the state of corrosion or possible corrosion of the part 22 can be obtained by highlighting a modification of the propagation of the optical signal in the fiber. As indicated above, the invention is however not limited to a detection element in the form of an optical waveguide. In order to illustrate this aspect, the following description sets out to describe, in connection with FIGS. 9 and 10, the case of a detection element in the form of an electrical conductor, for which the check is carried out in detecting a change in the propagation of an electrical signal, and no longer optical.

FIG. 9 thus represents a detection element 1a in the form of an electrical conductor which is able to allow the propagation of an electrical current in normal operation. The electrical conductor la can have any shape and can for example be in the form of at least one tab conductive as shown, or in the form of one or more wires in a variant not shown. The electrical conductor has a sheath surrounding the conduction portion. The electrical conductor 1a can be arranged with respect to the part 22 in the same way as illustrated in FIGS. 6 to 8. According to one example, the electrical conductor 1a comprises a conduction portion 3a, for example made of copper, in which are present a plurality of particles 10 encapsulating a modifying agent 12. The particles 10 are as described above. In the same way as described above, in the presence of a compound 16 associated with the corrosion of the part, the modifying agent 12 is released producing an elimination of at least part of the electrical conductor 1a (see FIG. 10). The modifying agent 12 can for example be an acid which makes it possible to dissolve a metallic conduction portion 3a, made of copper for example. It is then possible to detect the presence of the compound 16 associated with the corrosion using a control unit which is able to measure the change in resistance or resistivity of the detection element la, for example by balancing a resistive bridge like a Wheatstone bridge.

It is also possible to have a structure similar to that illustrated in FIG. 5 for the electrical conductor. In this case, the detection element may comprise an electrically conductive wire or cable in place of the core 3 and a sheath around it comprising the particles 10, such as the sheath 5 illustrated. According to this variant, the release of the modifying agent makes it possible to eliminate all or part of the conductive wire or cable, thus modifying the resistance or resistivity of the detection element.

There is shown in Figure 11 a variant of particles 100 which can be used in the context of the invention regardless of the nature of the detection element 1 and the. The particles 100 differ from the particles 10 previously described in that the wall 140 encapsulating the modifying agent 12 is multi-layered, here bi-layered, comprising a first internal layer 140a encapsulating the modifying agent 12, and a second external layer 140b around the first internal layer 140a. The first internal layer 140a is insensitive to the modifying agent 12, that is to say it is not affected by contact with the modifying agent 12. The second external layer 140b is nevertheless able to open on contact with modifying agent 12, for example modifying agent 12 may be a solvent for this layer 140b or be able to cause disintegration of the latter. The first inner layer 140a can be hydrophilic and the second outer layer 140b hydrophobic. The wall 140 can be formed by an amphiphilic polymer. In the absence of the compound 16 associated with the corrosion of the part, the modifying agent 12 is held in the particles 100 and is not released. It will be noted that compound 16 can come from single-layer particles as described above which therefore play, in this case, the role of initiators of the chain reaction.

FIG. 12 illustrates the diffusion of the compound 16 associated with the corrosion of the part in the particles 100. The compound 16 diffuses as far as the internal layer 140a and causes it to open, for example its disintegration, so as to release the modifying agent 12 as illustrated in FIG. 13. This release causes the modifying agent 12 to come into contact with the outer layer 140b, also resulting in its opening and the release of the modifying agent 12 outside the particles 100. FIG. 14 illustrates the cascade opening of a plurality of particles 100 following the opening initially of a single particle 100. The modifying agent 12 released by the first particle 100 which has been opened triggers a chain release of the modifying agent 12 in the other particles 100.

The modifying agent 12 opens the outer wall 140b of the other particles 100 and one can choose a wall 140 for which the opening of the outer wall 140b triggers the disintegration of the inner wall 140a. An example for this wall 140 is an amphiphilic diblock system comprising a hydrophilic block such as polyethylene glycol (PEG) and a hydrophobic block such as polycarbonate. In this case, the modifying agent 12 can be a hydrophobic compound contained in the particles and solvent of the hydrophilic block. An example of such a modifying agent 12 is toluene. It will also be noted that the modifying agent 12 can be a vector of the compound 16 associated with corrosion capable of triggering the opening of the internal layer 140a, in order to bring this compound 16 to the other particles 100. An element particularly sensitive detection device since the opening of a single particle 100 makes it possible to trigger in cascade the opening of other particles present in the detection element and thus to produce a very significant modification of the propagation of the physical signal in the conduction portion.

FIG. 15 illustrates an example of an assembly 201 according to the second embodiment of the invention implementing a detection element 11 in the form of an optical fiber. Elements identical to those described above are denoted by the same reference symbols and the associated description is omitted for the sake of brevity.

It is desired to evaluate the corrosion or the possibility of corrosion of a part 221. This part 221 is in contact with the detection element 11. A single detection element 11 has been shown in contact with the part 221 but does not depart from the scope of the invention when the part 221 is provided with a plurality of detection elements 11 in contact with it. Part 221 may, as illustrated, be in the form of a substrate 24 coated with one or more layers 261, 281 of coating. In the examples illustrated in FIG. 15 as well as in FIGS. 22 and 23, the layer or layers 261 are anti-corrosion layers, and the layer 281 is a layer of paint, optionally comprising an anti-corrosion primer and a finish of polyurethane, or simply an anti-corrosion primer. According to a variant not shown, the part can be in the form of an uncoated substrate. Whatever the embodiment considered, the substrate 24 can be metallic, for example steel, aluminum or aluminum alloy. In the case where the substrate 24 is made of steel, the anti-corrosion layer(s) 261 can be made of ZnNi, ZnFe, or be layers obtained by cadmium plating. In the case where the substrate 24 is made of aluminum or an aluminum alloy, the anti-corrosion layer(s) 261 may be anodization layers.

In each of the examples of assembly illustrated, the detection element 11 is in contact with at least one of the coating layers of the part 221, and in particular in contact with at least one anti-corrosion layer 261. It can be advantageous, as shown, that the optical fiber 11 is coated on its outer surface with a metal coating 7 (covering the sheath 5) in order to promote the adhesion of the fiber to an anti-corrosion layer 261 of the part. Coating 7 is as described above. According to a first example of an assembly 201 illustrated in FIG. 15, the optical fiber 11 is inserted between the anti-corrosion layer 261 and the paint layer 281. In this case, the optical fiber 11 can be in contact with the layer a nti -corrosion 261 and the paint layer 281. According to a second example of assembly 201a illustrated in Figure 22, the optical fiber 11 is inserted between the substrate 24 and the anti ^¬ corrosion layer 261. In this case, the fiber optical fiber 11 can be in contact with the anti-corrosion layer 261 and the substrate 24. According to a third example of an assembly 201b illustrated in FIG. 23, the optical fiber 11 is inserted between two anti- ^corrosion layers 261, and can be in contact with these two layers 261. The configurations of the first and third examples (FIGS. 15 and 23) make it possible to detect corrosion before attack on the substrate 24.

Unlike what has been described for the first embodiment, the second embodiment is remarkable in that the part 221 comprises the particles 10 encapsulating the modifying agent 12 making it possible to chemically eliminate a part thereof in contact with it. less of the sensing element 11. As indicated above, the modifying agent 12 is capable of being released in the presence of a compound associated with the corrosion of the part, which can be a product resulting from the corrosion of the part or an entity able to corrode the part and/or to catalyze this corrosion. The compound associated with the corrosion of the part likely to cause the release of the modifying agent is as described above. This release leads to a chemical elimination of at least part of the detection element 11 leading to an alteration of the propagation of the physical signal in the conduction portion 3. The particles 10 are present in a zone of the part in contact with the detection element 11. In the example illustrated, these particles 10 are housed in the anti-corrosion layer(s) 261 . It is not beyond the scope of the invention if these particles are present in the substrate 24 itself and/or in the paint layer 281 instead of or in addition to their presence in the anti-corrosion layer(s) 261 .

The particles 10 have been described above in connection with the first embodiment and the description given remains applicable to the second embodiment. realization, in particular with respect to the nature of the modifying agent 12 and of the wall 14.

The particles 10 are present in a zone of the part, here in the anti-corrosion layer(s) 261, and the sum of the external surfaces of the particles 10 per unit volume of said zone can be between 60 m ¹ and 6.10 ⁸ m ¹ . The particles 10 may be present over at least half the thickness of the anti-corrosion layer(s) 261, or even over substantially the whole of this thickness. The particles 10 can be uniformly dispersed in the volume of the anti-corrosion layer(s) 261. However, it is not beyond the scope of the invention if the distribution of the particles 10 is not uniform. It is for example possible to have a first concentration by volume of particles 10 in a first part of an anti-corrosion layer 261 located on the side of the detection element 11 which is greater than a second concentration by volume of particles (possibly zero) in a second part of the anti-corrosion layer 261 located on the side opposite the detection element. Such an example is advantageous because it participates in increasing the modification of the physical signal in the conduction portion during the release of the modifying agent, thus increasing the detection sensitivity.

FIG. 17 illustrates an example of a detection element 11 that can be implemented within the scope of the invention, useful for detecting corrosion or the possibility of corrosion of a part. In the example illustrated, the detection element 11 is an optical fiber which is illustrated, in FIG. 17 as well as in FIGS. 19 to 21, in cross section with respect to its longitudinal axis. The optical fiber 11 comprises a core 3 forming a conduction portion which is able to transmit an optical signal along the longitudinal axis of the fiber 11. The possible directions for the propagation of the optical signal SO are illustrated in FIG. forward relative to the drawing plane or backward relative to this plane). The details relating to the optical fiber described above (core, sheath, possible coating, manufacturing method, etc.) in connection with the first embodiment remain applicable. However, unlike what was described above, the particles 10 are not present in the fiber 11 but in the part 221.

FIG. 18 illustrates the particles 10 in contact with the compound 16 associated with the corrosion of the part, for example an H ⁺ ion or an OH ion or even an ion halide, which allows the release of the modifying agent 12. The compound 16 is present in the part 221, in particular in the anti-corrosion layer(s) 261. For example, when it is corroded, the anti-corrosion layer 261 can form hydroxides, for example zinc hydroxides, which cause the release of the encapsulated modifying agent, and the degradation of the optical fiber 11. Alternatively, the anti-corrosion layer 261 can be inert and the detection element 11 can simply detect an entity able to corrode the part and/or to catalyze this corrosion, such as an H ⁺ ion. One can advantageously choose a modifying agent 12 which attacks exclusively the material of the optical fiber 11, and in particular not the part 221, that is to say neither the substrate 24, nor a coating layer 261 or 281. The modified agent 12 released comes into contact with the detection element 11 and produces its chemical elimination. It can thus be seen in FIG. 19 that this release produces a chemical elimination of the sheath 5 of the optical fiber 11 by a dissolution or chemical reaction mechanism. The release of the modifying agent 12 can be due to a total or partial destruction of the wall 14 in contact with the compound 16. partial or total of this wall and the release of the encapsulated modifying agent 12. FIG. 20 shows the evolution over time of the chemical elimination of the optical fiber 11 as it comes into contact with the modifying agent 12 released. This bringing into contact results in a greater elimination of the sheath 5 than that illustrated in FIG. 19 so that the effect of modifying the optical signal is maximized without disturbing the heart 3 which is here made of another material, insensitive. to the modifying agent 12. FIG. 21 illustrates a variant of FIG. 20 in which there is, in addition to the total or partial elimination of the sheath 5, a total or partial elimination of the core 3. The alteration of the optical fiber 11 produced following contact with the modifying agent 12 released can lead to a rupture of the optical fiber 11, or simply to damage to the latter, which can be demonstrated by detecting a modification of the propagation of the optical signal compared to the situation before the release of the modifying agent. In general, the presence of particles 10 in the part 221 is determined so as to obtain a detectable modification of the propagation of the optical signal, following the release of the modifying agent 12. The choice of the diameters of the core and of the cladding, in combination with the wavelength chosen, will determine the distribution of optical power between the core of the cladding. It is possible to favor relatively thin sheaths so as to ensure that the modifying agent 12 released will be present in a zone of size comparable to the extent of the optical mode in the sheath 5, in order to be able to easily detect the modification of the propagation of the optical signal without having to alter the heart 3. The heart 3 can nevertheless be altered if a strong modification of the propagation of the optical signal is sought, in order to facilitate detection. In general, the person skilled in the art knows how to determine, using his general knowledge, the dimensions of the core 3 and of the sheath 5 to be adopted as well as the distribution of the particles 10 in the part 221, so as to obtain a modification detectable optical signal propagation.

The assembly 201 further comprises a control unit 30 or "interrogator" which is capable of detecting the modification of the propagation of the physical signal in the conduction portion following the chemical elimination of said at least part of the element detection 11 by the modifying agent 12. The control unit 30 has been described in connection with the first embodiment and the description given remains applicable.

Analogously to what has been described above, FIG. 24 represents a detection element 11a in the form of an electrical conductor which is capable of allowing the propagation of an electrical current in normal operation and of experiencing a change in resistance or resistivity in the presence of a compound associated with corrosion. It will also be noted that the variant relating to the particles 100 with a multilayer wall 140 described in connection with FIGS. 11 to 14 remains applicable to the second embodiment.

The expression "between ... and ..." must be understood as including the limits.

Claims

[Claim 1] Detection element (1; la) of corrosion or the possibility of corrosion of a part (22), the detection element comprising a conduction portion (3; 3a) able to transmit a physical signal (SO), the sensing element being characterized by incorporating particles (10) encapsulating a modifying agent (12) which is capable of being released in the presence of a compound (16) associated with corrosion of the part, said modifying agent being able, when it is released, to chemically eliminate at least part of the detection element so as to modify the propagation of the physical signal in the conduction portion.

[Claim 2] A sensing element (1; la) according to claim 1, wherein the modifying agent (12) is capable, upon release, of dissolving said at least part of the sensing element.

[Claim 3] Detection element (1; la) according to claim 1 or 2, in which the modifying agent (12) is capable, when it is released, of consuming by chemical reaction said at least part of the element of detection.

[Claim 4] A sensing element (1; la) according to any one of claims 1 to 3, wherein the particles are present in said at least part of the sensing element and the sum of the outer surfaces of said particles added the volume of said at least one part being between 60 rrf ¹ and 6.10 ⁸ m ¹ .

[Claim 5] A sensing element (1; la) according to any one of claims 1 to 4, wherein the particles (100) comprise a wall (140) encapsulating the modifying agent (12), said wall comprising a first inner layer (140a) insensitive to the modifying agent and able to open in the presence of the compound (16) associated with the corrosion of the part to release the modifying agent, and a second outer layer (140b) able to open on contact with the modifying agent.

[Claim 6] A sensing element (1) according to any one of claims 1 to 5, wherein the sensing element is an optical waveguide.

[Claim 7] A sensing element (1) according to claim 6, wherein the sensing element is an optical fiber.

[Claim 8] Detection element (1) according to claim 7, in which the optical fiber comprises at least one core (3) forming a conduction portion capable of transmitting an optical signal (SO), and a sheath (5) surrounding the core, and wherein the particles (10) are present in at least one of the core and the sheath.

[Claim 9] A sensing element (la) according to any one of claims 1 to 5, wherein the sensing element is an electrical conductor.

[Claim 10] Assembly (20; 20a; 20b) for detecting corrosion or the possibility of corrosion of a part (22), comprising at least:

- a detection element (1; la) according to any one of claims 1 to 9,

- a part (22) in contact with the detection element, and

- a control unit (30) capable of detecting the modification of the propagation of the physical signal in the conduction portion (3; 3a) following the chemical elimination of said at least part of the detection element by the modifying agent (12).

[Claim 11] An assembly (20; 20a; 20b) according to claim 10, wherein the part (22) is an aircraft part.

[Claim 12] Method for detecting corrosion or the possibility of corrosion of a part (22) implementing an assembly (20; 20a; 20b) according to claim 10 or 11, comprising at least:

- the detection of a possible modification of the propagation of the physical signal (SO) in the conduction portion (3; 3a) using the control unit (30), and

[Claim 13] Assembly (201; 201a; 201b) for detecting corrosion or the possibility of corrosion of a part (221), comprising at least:

- a detection element (11; 11a) comprising a conduction portion (3; 3a) capable of transmitting a physical signal (SO), and

- a part in contact with the detection element, said part incorporating particles (10; 100) encapsulating a modifying agent (12) which is able to be released in the presence of a compound (16) associated with the corrosion of the part, said modifying agent being able, when released, to chemically eliminate at least part of the sensing element so as to modify the propagation of the signal physics in the conduction portion.

[Claim 14] Assembly (201; 201a; 201b) according to claim 13, in which the modifying agent (12) is capable, upon its release, of dissolving the said at least part of the sensing element (11) .

[Claim 15] Assembly (201; 201a; 201b) according to claim 13 or 14, in which the modifying agent (12) is capable, when it is released, of consuming by chemical reaction said at least part of the element detection (11).

[Claim 16] Assembly (201; 201a; 201b) according to any one of claims 13 to 15, in which the particles (10; 100) are present in at least one zone (261) of the part and the sum of the surfaces of said particles relative to the volume of said at least one zone being between 60 m ¹ and 6.10 ⁸ m ¹ .

[Claim 17] An assembly (201; 201a; 201b) according to any one of claims 13 to 16, wherein the particles (100) comprise a wall (140) encapsulating the modifying agent (12), said wall comprising a first inner layer (140a) insensitive to the modifying agent and able to open in the presence of the compound (16) associated with the corrosion of the part to release the modifying agent, and a second outer layer (140b) able to open on contact with the modifying agent.

[Claim 18] An assembly (201; 201a; 201b) according to any of claims 13 to 17, wherein the sensing element (11) is an optical waveguide.

[Claim 19] An assembly (201; 201a; 201b) according to claim 18, wherein the sensing element (11) is an optical fiber.

[Claim 20] An assembly (201; 201a; 201b) according to any one of claims 13 to 17, wherein the sensing element (11a) is an electrical conductor.

[Claim 21] Assembly (201; 201a; 201b) according to any one of claims 13 to 20, in which the part (221) comprises a substrate (24) coated with at least one layer (261; 281) in which the particles are present, the detection element (11) being in contact with said at least one layer.

[Claim 22] An assembly (201; 201a; 201b) according to claim 21, wherein the layer (261) is an anti-corrosion layer.

[Claim 23] An assembly (201; 201a; 201b) according to claim 21 or 22, wherein the layer (261; 281) is a paint layer.

[Claim 24] An assembly (201; 201a; 201b) according to any one of claims 13 to 23, wherein the part (221) is an aircraft part. [Claim 25] Assembly (201; 201a; 201b) according to any one of claims 13 to 24, in which the assembly further comprises a control unit (30) capable of detecting the modification of the propagation of the physical signal ( SO) in the conduction portion (3) following the chemical elimination of said at least part of the detection element (11) by the modifying agent (12). [Claim 26] Method for detecting corrosion or the possibility of corrosion of a part (221) implementing an assembly (201; 201a; 201b) according to claim 25, comprising at least:

- the detection of a possible modification of the propagation of the physical signal (SO) in the conduction portion (3) using the control unit (30), and