WO2009007395A1

WO2009007395A1 - System, method and sensor for monitoring the impairment of materials by moisture

Info

Publication number: WO2009007395A1
Application number: PCT/EP2008/058918
Authority: WO
Inventors: Philippe Gegout; Fabien Barberon; Stan Leclerc; Regis Sarcia; Julien Lopez-Rios
Original assignee: Bouygues Travaux Publics
Priority date: 2007-07-09
Filing date: 2008-07-09
Publication date: 2009-01-15
Also published as: FR2918750A1; FR2918750B1; EP2167936A1

Abstract

System, method and sensor for monitoring the impairment of materials, comprising a monitoring device (1,16) and a sensor (2), said sensor (2) having means (7, 19, 20) for connection to the monitoring apparatus (1, 16), in which the sensor (2) comprises a corrosion-resistant substrate (9) on which a metallic element (10) is applied, said metallic element (10) having a surface finish suitable for monitoring the localized initiation of the corrosion of said metallic element and, where appropriate, the propagation of said corrosion.

Description

SYSTEM, METHOD, AND SENSOR FOR CONTROLLING ALTERATION OF WET MATERIALS

A system, method and sensor for controlling wet weathering of materials for the prevention of degradation of architectural structures, means of transport or any type of metal-based structure or wood.

These materials based on wood or metal are altered during their cycle of use due in particular to aggression of environmental elements, in particular water.

In the context, for example, of the construction of architectural work, metal reinforcements are cast in concrete.

These reinforcements are prone to corrosion due to the penetration, through the porous surface of the concrete, of active agents such as sodium chlorides or carbon dioxide.

These aggressive agents have the effect of causing corrosion of these reinforcements during a process called carbonation.

These reinforcement corroding increase in volume, and cause the bursting of the concrete coating, causing serious structural damage, and therefore reducing the life of these structures.

Similarly, for a wooden architecture work alterations relating to rot and mildew are generated by moisture and weather.

A problem arises then to be able to control the state of these frames to prevent or follow these different alterations.

It is known in the field of the construction of concrete architecture work to conduct a regular inspection of the metal frames.

This inspection is carried out from operations of degradation of concrete blocks embedding these frames, in order to be able to control their state by a visual access. Similarly, for wooden structures, inspection inspections can be carried out from sampling, intended to be analyzed, or taking measurement of the moisture content of the wood.

But such inspections are of a destructive nature for these works, because of the material damage created by operations of degradation, sampling or taking measurements. Moreover these inspections generate many constraints for their implementation.

To overcome these drawbacks, patent document US5015355 teaches a system comprising a sensor placed in embedding concrete, located between the first reinforcing layer and the surface of the architectural structure. This sensor consists of at least one steel anode of composition close to the metal frames and a reference cathode. This sensor is connected to a device for carrying out galvanometric measurements by wire links. After a depassivation of the anode by the aggressive agents, the interstitial solution of the concrete behaves like an electrolytic solution, and a current of electrons appears between the anode and the cathode. This current is then measured. The intensity obtained makes it possible to determine a measurement of the corrosion of the anode and indicates the risk of deterioration incurred by these reinforcements.

However, the values of these measurements are unreliable. The humidity and / or the temperature of the environment in which the structure is exposed make these measurements unusable, if they are not renewed regularly and are not corrected according to the climatic history of this environment.

In addition the aggressive agents penetrate into the concrete to reinforcement from channels arranged for the passage of the wire links connecting the sensor to the measuring device, which has the major drawback of artificially accelerating the degradation of the reinforcements.

In the publication document "Wireless threshold sensors for detecting corrosion in reinforced concrete structures", from the magazine "Smart structures and materials 2006", authored by Dickerson, Andringa, Puryear, Wood and Neikirk, a system of measure of which the mechanism is different from those mentioned above. This system includes a sensor connected by a wireless link to a device related to a read coil. This sensor corresponds to a resonant circuit consisting of a metal element which is connected to the terminals of an induction coil, said coil being connected in series with a capacitance. The sensor is placed in the embedding concrete. When the metallic element is corroded, the resonance properties of the sensor are modified. From the measurement of the resonance, taken at a distance, the corrosive state of the concrete is determined on the basis of a single measurement making it possible to assess the risk of corrosion to which these reinforcements are exposed.

However, the corrosion of the metal element of the sensor is initiated randomly. Indeed, for two metallic elements placed under the same conditions, corrosion develops in a number of completely different points. A metallic element where the corrosion is distributed in a large number of points will offer, compared to another metallic element where the corrosion is localized at a single point, a totally different resistance and therefore an erroneous measurement on the corrosive state of the medium where it is located.

The disadvantage of such a system lies in the fact that the measurements made do not make it possible to quantify the exact level of corrosion of the medium. Consequently, such a system does not make it possible to obtain reproducible and reliable measurements.

Another sensor is described in DE 20 2006 009541, but it also does not allow to quantify the corrosion of the medium. The present invention aims to solve this problem of reproducibility of the measurements made and to make these measurements reliable, thanks to a sensor where the location of the initiation of the corrosion, and then the propagation thereof, is controlled.

More specifically, the subject of the invention is a material alteration control system comprising a control apparatus and a sensor, said sensor comprising connection means with the control apparatus, in which the sensor comprises a corrosion-resistant substrate to which a metal element is applied, said metallic element having a surface state adapted to control the location of the initiation of its corrosion and, if appropriate, the propagation of this this. For example, the surface of the metal element for this purpose comprises at least one discontinuity. In particular, it advantageously comprises an etching which makes it possible to control the initiation and the propagation of the corrosion of the metallic element, in order to determine from a single measurement the corrosive nature of the medium in which it is located. The control of the initiation of this corrosion on the surface of the metallic element thus makes it possible to have a reliable and reproducible measurement. According to particular embodiments: the control apparatus is radio detection equipment; the recording equipment is a radio frequency transceiver equipment; the recording equipment is electrical equipment for performing inductive measurements; the sensor comprises two connection terminals connected to an electronic module for impedance measurement; the control device comprises an electronic module for measuring impedance; the connection means are wireless and relate to at least one transmission module, for transmitting at least one electromagnetic wave towards the sensor, and at least one receiving module for receiving at least one electromagnetic wave coming from the sensor; the connection means are wired and refer to metal cables connecting said control device to the connection terminals of the metal element of the sensor or to the electronic impedance measurement module; the electronic impedance measurement module comprises a communication sub-module for radiofrequency transmission and reception; the communication sub-module is an RFID chip (meaning "radio frequency identification"); the radio detection equipment is a radar; the metallic element is a metal layer or wire; The invention also relates to a sensor included in a material alteration control system comprising a corrosion resistant substrate to which a metal element is applied, said metal element having a surface state adapted to control the location of the initiation of its corrosion and, if appropriate, the propagation thereof.

According to particular embodiments: the surface comprises at least one discontinuity, the surface comprises at least one etching formed on the surface of the metal element; the metallic element has a thickness allowing optimal reflection of at least one electromagnetic wave; the metal element comprises two connection terminals; the substrate is plastic or ceramic, the substrate is able to absorb the mechanical stress that is induced by the expansion of the metal element during corrosion.

The invention also relates to a method for controlling the deterioration of materials, comprising the following steps: transmission of at least one electromagnetic signal towards a metal element of a sensor by a control device, signal processing electromagnetic by a metal layer of the sensor, - reception of the electromagnetic signal by the control device, determining a measurement of the corrosion of the metal layer by the control device from the received electromagnetic signal.

Advantageously, the electromagnetic signal is an electromagnetic wave or an electric current.

According to particular embodiments of the steps: the treatment comprises at least one step of reflecting the electromagnetic wave on the metal element; in this case the measurement of the corrosion is a function of the amplitude of the electromagnetic wave, in particular of the radar echo, received by the reception module included in the control apparatus, said electromagnetic wave amplitude varying in inverse function of the progression of the state of corrosion of said metallic element; the treatment comprises at least one step of passing electrical current through the metal element; in this case, the measurement of the corrosion is a function of the intensity of the electric current received by the said control apparatus, the said intensity of the received current varying inversely with the progression of the state of corrosion of the metallic element.

Other characteristics and advantages of the invention will emerge from the following reading of a nonlimiting exemplary embodiment, with reference to the appended drawings which represent, respectively: FIG. 1, embodiment of the invention with a measurement by impedance measurement in a reinforced concrete architecture structure; Figure 2 is a schematic view of an embodiment of a sensor; Figure 3, a sectional view of the sensor; Figure 4 is a schematic view of the corrosion of the sensor; FIG. 5, embodiment of the invention with an impedance measurement in a wooden architecture structure; FIG. 6, a graphical view of the evolution of the resistance of the sensor as a function of the thickness of the metal layer; FIG. 7, embodiment of the invention with an electromagnetic wave measurement in a reinforced concrete architecture structure; FIG. 8, embodiment of the invention with an electromagnetic wave measurement in a wooden architecture structure; FIG. 9 is a graphical view of the evolution of the amplitude of the electromagnetic wave reflected as a function of the thickness of the metal layer.

With reference to FIG. 1, the control system comprises a corrosion sensor 2 and a control device 1.

The sensor 2, at the terminals 11 and 12, is connected to an electronic module for measuring impedance 3. The electronic module comprises a communication sub-module 8 of RFID chip or NFC / RFID type for recording measurement data and to transmit this data or to receive other data by radiofrequency when it is in the presence of the control device 1 corresponding to an RFID reader or NFC / RFID (acronym for "Radio Frequency Identification / Near Field Communication" which can result in a radio identification system from a near-field communication).

This sensor 2 therefore exchanges data with the control device 1 via the electronic module 3 and its communication sub-module 8 from wireless means.

However, in another embodiment, this electronic module for measuring impedance 3 is included in the control device 1.

This module 3 is then connected to the connection terminals 11 and 12 of the sensor 2 by wire means such as metal cables. This sensor 2 illustrated in Figure 2 and Figure 3, comprises a substrate 9 made of a non-metallic material such as plastic, or ceramic.

This substrate 9 is insensitive to corrosion and has a planar geometry with a thickness of between 1 mm and 3 mm and a lateral dimension of less than 5 cm.

On the surface of this substrate 9 is applied a metal element 10, for example in the form of a metal layer of thickness 24 between 20μm and 500μm. The application of the metal layer on the surface of the substrate 9 can be carried out in various ways known to those skilled in the art, such as: vapor phase deposition, interlocking, and bonding. The geometry of the substrate is not exclusive: it can thus be spherical, cylindrical or plane, with a thickness of between 100 μm and 1 cm depending on the geometry chosen.

In addition, the metal element 10 is in another embodiment a metal wire, applied to the substrate by winding and / or bonding to the substrate 9.

The thickness 24 of the metal element 10 makes it possible to control the sensitivity to corrosion that is desired and to adapt to the control apparatus used for the measurement.

The metal element 10 has a surface state adapted to control the location of the initiation of corrosion and the propagation thereof.

As will be seen below, a discontinuity (that is to say a sudden variation of relief) of the surface of the metal element promotes the initiation of corrosion at the level of this discontinuity. This discontinuity can be in a point form (peak or hollow) or in a two-dimensional form (for example, an elongated stripe).

The discontinuity must have sufficient amplitude to promote the initiation of corrosion. For example, in the case of a scratch made on the surface of the metal element, its depth is typically between 1 and 50 microns.

Moreover, the discontinuity must constitute a net change of orientation of the surface, resulting in a sharp angle between the surface and the discontinuity. By this is meant that at the point of connection between the surface of the metallic element and the discontinuity, the tangent to the surface of the metallic element and the tangent to the discontinuity are not merged.

Once initiated at the discontinuity level, corrosion tends to propagate from it. For example, in the case where a scratch is formed on the surface of the metal element, the corrosion will initiate at one or more points of the scratch, then spread along it, before spreading into the metal. thickness of the metal element.

In addition to controlling the location of the initiation of corrosion, the discontinuity may also have a function of controlling the propagation of corrosion, allowing the guide thereof.

A surface state that is well suited to the implementation of the invention corresponds, for example, to an etching 21 performed in at least one point by: mechanical or laser machining mechanisms, - chemical application, deposition on the passive surface with or without a layer, or a combination of these different processes.

Etching being obtained by techniques well mastered by those skilled in the art, it constitutes a particularly advantageous embodiment of the invention, but it is understood that the formation, on the surface of the metal element, of least an asperity on which the corrosion would be initiated preferentially, could be considered without departing from the scope of the invention.

During the construction of an architectural structure the sensor 2 is preferably placed in the concrete 6. The placement of this sensor is made so that the metal layer is in contact with the interstitial solution of the concrete.

Advantageously, the sensor will be poured into the concrete at the time of the realization of the structure.

The sensor 2 illustrated in FIG. 2 presents an etching topology which makes it possible to obtain a generally uniform corrosion of the metal layer of the sensor.

This topology 22 consists of etchings 21 which form a set of rectilinear and parallel grooves arranged perpendicularly with another set of rectilinear and parallel grooves so as to form a matrix of etchings 22.

This matrix 22 then constitutes a grid topology 22.

The spacing between each of the parallel grooves is between 100μm and 5mm. In this embodiment this spacing is set at 1 mm.

However, it goes without saying that another topology (for example points, parallel stripes, etc.) can be adopted without departing from the scope of the present invention.

Those skilled in the art may indeed define the most appropriate topology depending on the conditions of use of the sensor.

It is known in the field of construction that concrete, material made from cement paste, is a porous material partially filled with an interstitial solution.

In reinforced concrete, the metal reinforcements are in contact with this interstitial solution.

In a young cement, the composition of the interstitial solution is such that the reinforcements are protected against corrosion, it is the passivation phenomenon. However, aggressive agents such as carbon dioxide (CO2) or chloride ions (Cl-) can penetrate the concrete depending on the environmental conditions to which the architecture is subject.

The rate of progression of these aggressive agents can be up to five millimeters per year.

These aggressive agents react in the interstitial solution. The pH (acronym for the potential hydrogen terms, which makes it possible to measure the acidity or the basicity of a solution) of this solution decreases.

However, below a threshold value of the pH, the metal reinforcements are no longer protected against corrosion because the passivation layer disappears.

When the aggressive agents reach the metal reinforcements they thus generate a corrosion of these reinforcements. The corroded reinforcements inflate and thus generate serious structural problems reducing the life of the building. The typical diameter of the frames is between 6mm and 12mm.

However, corrosion of only 100 μm deep has disastrous consequences.

To prevent such problems, the sensor 2 is then placed in the concrete 6 of coating between the metal frames 4 and the external surface of the architectural work 5.

When the physicochemical conditions of the concrete 6 in which the sensor 2 is placed become favorable for corrosion, a potential difference appears between the metal layer 10 and the interstitial solution.

Although the potential of the metal layer is uniform, the angular portions 23 present at the edges of the etchings 21 induce a local increase of the electric field.

Surrounding ions migrate to these strong field areas. These electric fields and these ion concentration gradients can theoretically be calculated by means of the Poisson-Boltzmann equation whose boundary conditions are defined by the surface geometry of the metal layer 10. Because of this migration of the ions towards the etchings 21, the conditions are then more corrosive in the vicinity of the etchings 21 where will therefore proceed the reaction transformation of the metal into oxides.

The higher the angular parts of the engravings, the more this phenomenon is accentuated. Thus a surface state comprising etching makes it possible to initiate and guide the corrosion of the metal element.

In addition, in the various embodiments implementing the invention, the electromagnetic signal used relates for example to electromagnetic waves, electric currents, or even radio waves.

During a procedure for checking the deterioration of the metal reinforcements, the RFID reader 1 is approached to the surface 5 of the architectural structure behind which are the sensor and the electronic module impedance measurement. The RFID reader 1 sends a radio frequency signal towards the communication sub-module, ie the RFID chip 8.

On receipt of this signal, the RFID chip sends an interrogation request to a processing sub-module, not shown, included in the electronic measurement module so that the resistance at the connection terminals 11, 12 of the sensor is determined. The measurement being carried out, the processing sub-module sends a response to the request comprising the value of this measurement to the RFID chip 8 which then transmits this response to the RFID reader 1 by a radio frequency signal.

Note that the determination of the resistance is obtained by the application to the connection terminals 11, 12 of a voltage to obtain an intensity value. The resistance is thus deduced from the following formula:

U = RI, with: - the voltage applied to the connection terminals 11, 12 of the sensor, R the resistance of the metal layer to determine the strength of the metal layer 10, and

I, the intensity of the measured current passing through the metal layer 10. It is noted that the intensity of the current varies inversely with the progression of the state of corrosion of the metal element.

For several measurements, the more the intensity values recorded decrease the more the metal element is corroded and the value of the resistance of the metal element increases.

The measurement of the resistance of the metal element makes it possible to deduce the thickness of the non-corroded metal element.

It is noted that a single measurement makes it possible to determine the state of corrosion of the metal element.

Measurements can be programmed to be performed regularly and recorded in memory means of the module. These measurements will subsequently be transmitted to the RFID reader 1 during a query.

The program for performing regular measurements or measurements at a given date is made from a computer and is then downloaded into memory means of the RFID reader 1. Thereafter this program is transferred to the memory means of the electronic measurement module from the RFID chip 8.

The measurement carried out makes it possible to determine the thickness 24 of non-corroded metal remaining since the installation of the sensor in the architectural structure. This change in the thickness 24 of the metal layer reflects the progress of the corrosion reaction of the metal layer of the sensor. This measure will therefore be used to evaluate the condition of the structure locally.

In order to improve the measurements, the electronic impedance measuring module 3 may comprise a reference resistor for making differential measurements and other sensors, such as a temperature and instantaneous humidity sensor. In Figure 4 is presented the corrosion of the sensor 2.

Between times t0 and t1 the physicochemical conditions became locally favorable to corrosion.

Unlike a metal element having a smooth surface, on which the corrosion initiates randomly, the metal element having scratches is subjected to corrosion which initiates in a controlled manner.

On the sensor 2, the dissolution of the metal and the formation of oxides is thus initiated in a localized manner at the level of the scratches. In addition, in the case of a grid topology, corrosion is generally uniform over the metal surface of the sensor.

If the local conditions are always favorable to corrosion, there is an increase in corrosion which simply results in a progressive decrease of the thickness 24 as a function of time, of the uncorroded metal layer, until the complete disappearance of the that is from t1 to t5.

It is noted that the presence of at least one etching is sufficient to initiate and guide corrosion on the metal layer.

The life of the sensor depends on the rate of corrosion, which is related to the surface condition (for example, in the case of an engraving, the more pronounced and / or deep, the faster the corrosion will be, and conversely) and the thickness of the metal element.

Those skilled in the art will therefore size the sensor so that it has a lifetime adapted to reflect the corrosion of the architectural work for the desired duration.

In Figure 5, the same device described in Figure 1 can be implemented for a wooden architecture. The sensor 2 is placed between the inner wall 13 and outer 15 of a structure subject to the risk of alteration by moisture and water that causes the rotting of wood. If there is an insulation layer 14 between the inner wall 13 and the outer wall

15, in this case the sensor 2 is placed between the insulation layer 14 and the wall 13. This placement of the sensor 2 made in this way is not limiting.

One of the factors in the corrosion phenomenon of the metal element 10 of the sensor 2 is the presence of water, thus the thickness 24 of the metal element 10 of the sensor 2 is correlated with the exposure history of the sensor 2. moisture experienced by the inner wall 15.

The advantage of measuring the thickness of uncorroded metal 24 is that a single measurement provides information on the entire history of exposure to moisture of the structure. FIG. 6 shows the evolution of the resistance "R" d of the metal layer of the sensor as a function of the thickness 24 "e" of this non-corroded metal layer. Theoretically the resistance "R" of a metallic parallelepiped follows the following formula:

with:

p corresponding to the resistivity of the metal constituting the metal layer,

- L, I and e respectively relating to the length, the width and the thickness 24 of the metal layer from the etchings, and by performing a grid topology 22, the corrosion reaction guided spatially so that corrosion results globally to a simple evolution of the thickness 24 "e" whereas "L" and "I" remain little changed.

The formula then remains valid during the life of the sensor, unlike a sensor having a smooth surface state where the corrosion is spatially random on the metal layer.

Consequently, the resistance measurement made by the impedance measurement module (32) makes it possible to deduce the thickness 24 "e" of the remaining metal layer, during the course of the corrosion progression 26. In FIG. 7, another embodiment of the invention teaches a control system comprising a sensor 2, with a grid topology 22, and a control device 16.

This sensor is placed in the concrete 6, between the frames 4 and the surface of the architectural work 5.

This control device is a radio detection equipment such as a radar.

This system makes it possible to measure the reflection of electromagnetic waves by the metal layer 10 of the sensor 2. This radar 16 comprises a transmission module 17 of at least one electromagnetic signal 20 and a reception module 18 of at least one signal electromagnetic 21 as well as modules for data processing and storage of measurements.

During a control procedure of the state of this sensor the radar is oriented towards the surface 5 of the structure where the sensor 2 is located. The emission module 17 emits at least one electromagnetic wave 20 and more. particularly propagating electromagnetic pulses.

These propagating electromagnetic pulses are reflected by the metal layer of the uncorroded sensor when they come into contact with the sensor. These reflected propagating electromagnetic pulses 19 are received by the reception module 18 and thus an electromagnetic echo, the radar echo, is detected.

The amplitude of the electromagnetic pulses received by the receiving module varies inversely with the progression of the corrosion state of the metallic element.

For several measurements made, the more the amplitude of the electromagnetic wave, and in particular the radar echo, received for each of the measurements decreases the more the metal layer is corroded.

Thus these measurements make it possible to determine the thickness of the remaining metal layer, that is to say the thickness of the non-corroded metal layer. It is noted that a single measurement makes it possible to determine the state of corrosion of the metal layer.

This detection of the sensor 2 and in particular of the metal layer 10 depends mainly on the thickness 24 of the metal layer 10 applied to the substrate 9 and an electromagnetic quantity called skin thickness δ, the determination of which depends on the equation next :

with:

p and μ _R respectively relating to the resistivity and relative permeability of the metal layer,

- / corresponding to the frequency of the electromagnetic wave sent by the transmission module,

- μ ₀ relating to the constant of absolute permeability.

In FIG. 8, the control system comprising a radar and a sensor with a grid topology 22 is implemented in a wooden architecture structure.

The sensor 2 is placed between the inner wall 13 and outer 15 of a structure subject to the risk of alteration by moisture and water that causes the rotting of wood. Between the inner wall 13 and outer wall 15, if there is an insulation layer 14, in this case the sensor 2 is placed between the insulation layer 14 and the inner wall 13. This placement of the sensor 2 made of this way is not limiting.

According to the same process, reflected propagating electromagnetic pulses 19 are received by the radar receiving module 18 and a radar echo is detected.

FIG. 9 illustrates the evolution of the amplitude of the electromagnetic echo detected as a function of the ratio between the thickness "e" 24 of the layer non-corroded metal and the skin thickness "δ", during the phase of progression of corrosion 26 of the metal layer.

For any metallic element such as the plane metallic layer probed by the radar echo of duration Mf, it behaves as a perfect mirror as soon as the thickness of the plane is greater than the skin thickness δ.

For an electromagnetic pick emitted by the emission module, of a value of giga hertz, the skin thickness in the metal and in particular in iron is less than one micron.

For a value of 5OkHz, the skin thickness is of the order of 10 .mu.m. When the metal layer of the sensor is completely corroded, oxides have replaced the metal layer.

There is no more skin thickness and the oxidized metal layer no longer has the reflective property of electromagnetic waves. Then, the sensor is no longer detected and therefore no longer generates significant echo at the receiving module.

In intermediate states between a non-corroded metal layer and a completely corroded metal layer, the intensity of the echo received makes it possible to determine the corrosion state of the sensor.

It is noted that without control of corrosion from a particular etching topology, the metal layer of the sensor would present partial and non-uniform corrosions, and therefore not reproducible which does not allow to obtain reliable measurements. The grid topology makes it possible to obtain an amplitude related to the thickness of the metal layer; other topologies where the metal layer is not continuous are possible. The embodiments described above are not limiting, other modes using direct electromagnetic techniques can be used.

Another embodiment using direct electromagnetic techniques can be obtained using inductive techniques where the control apparatus (16) consists of a set of coils capable of generating a time-varying magnetic field. The generated magnetic field interacts with the magnetic properties of the metal layer 10 of the sensor, which has the effect of either modifying the primary field, or to create a second one. The tester measures either the magnetic field reluctance or the coil impedance variation induced by the eddy currents generated at the surface of the steel by the application of the magnetic field. These two quantities are sensitive to the thickness of the uncorroded metal layer, therefore they are sensitive to the corrosion state of the sensor.

In the embodiments of the invention allowing impedance and electromagnetic reflection control, the control apparatus permits the collection of measurements and contains a data processing module and a memory module.

If sensors are placed at different depths and at different points in the architecture, then the tester can be used to probe a large number of sensors included in the architecture.

The described system comprises a database comprising information in the form of recorded data relating to the penetration depth of the aggressive agents at different points of the architectural work. The sensors include a radio frequency identification system as well as control devices.

The data identifying these sensors and these control devices are archived in the databases as well as the measurement data made from the control devices and the sensors. Thanks to these data, the book manager can carry out a preventive follow-up of the book.

In addition the book may be provided with an archiving memory information relating to the measurements made.

Regular transfers of data from control devices to the memory of the book can gather all the data about the book in the book's memory. In addition, the use in embodiments embodying the invention of control devices described above is not limiting.

The invention is not limited to the only cases of the systems described above. It can be used, for example, to control the corrosive risk of metal tubes used to consolidate oil or gas wells, or to control the corrosive risk of pipes carrying petroleum, chemical or gas products at a distance. . In addition, this system can also be applied to other materials that are susceptible to deterioration due to corrosive agents.

Claims

A sensor for a material alteration control system, comprising a corrosion-resistant substrate (9) to which a metal element (10) is applied, characterized in that said metallic element has a surface condition adapted from in order to control the location of the initiation of its corrosion and, if necessary, the propagation thereof.

2. Sensor according to claim 1, characterized in that said surface state comprises at least one discontinuity.

3. Sensor according to claim 2, characterized in that said surface state has at least one etching.

4. Sensor according to one of the preceding claims, characterized in that said metal element is a metal layer.

5. Sensor according to one of the preceding claims, characterized in that said metal element is a metal wire.

6. Sensor according to one of the preceding claims, characterized in that said metal element (10) comprises at least two connection terminals (11, 12).

7. Sensor according to one of the preceding claims, characterized in that the substrate (9) is plastic or ceramic.

8. Sensor according to one of the preceding claims, characterized in that said metal element (10) has a thickness adapted to reflect the electromagnetic waves.

9. Material alteration control system comprising a control apparatus (1, 16) and a sensor (2), said sensor (2) having connection means (7, 19, 20) with said control apparatus (1, 16), characterized in that said sensor (2) is a sensor according to one of the preceding claims.

10. System according to the preceding claim, wherein said control apparatus (16) comprises a radio frequency transceiver or an electrical equipment for measuring impedance.

11. A method of controlling the deterioration of materials, characterized in that it comprises the following steps: transmission of at least one electromagnetic signal in the direction of a metal element of a sensor (2) according to one Claims 1 to 8 by a control device (1, 16), processing said electromagnetic signal by a metal element (10) of said sensor (2), receiving said electromagnetic signal by said control device (1, 16), determining the a measurement of the corrosion of said metallic element by said control device (1, 16), from said received electromagnetic signal.

12. The method of claim 11, characterized in that said electromagnetic signal is an electromagnetic wave and in that said processing comprises at least one step of reflecting said electromagnetic wave (19,20) by said metal element (10).

13. The method of claim 11, characterized in that said electromagnetic signal is an electric current and in that said treatment comprises at least one step of passing said electric current into said metal element (10).