Method for determining a physical property of a substrate coating by electrochemical measurement
The method exposes coatings to a redox species for impregnation and electrochemical measurement, addressing inaccuracy and destructiveness of existing methods by precisely determining porosity and permeability, thus assessing corrosion risk effectively.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Applications
- Current Assignee / Owner
- COMMISSARIAT A LENERGIE ATOMIQUE ET AUX ENERGIES ALTERNATIVES
- Filing Date
- 2024-12-04
- Publication Date
- 2026-06-05
AI Technical Summary
Existing methods for determining the porosity and permeability of coatings on metallic substrates are inaccurate and often destructive, failing to provide sufficient precision for evaluating corrosion risk.
A method involving exposing the coating to a solution containing a redox species as a probe, allowing the species to penetrate and impregnate the coating, followed by electrochemical measurement of the extracted species to determine the coating's physical properties such as porosity and permeability.
Provides accurate and non-destructive determination of coating porosity and permeability, enabling effective assessment of corrosion risk and coating degradation.
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Abstract
Description
Title of the invention: Method for determining a physical property of a substrate coating by electrochemical measurement Technical field of the invention
[0001] The invention relates to the field of corrosion risk analysis of a substrate, typically a metallic substrate, protected by a coating.
[0002] More particularly, the invention relates to the determination of a physical property of the coating, for example its porosity or permeability in order to analyze corrosion risks. Technical background
[0003] Corrosion of metallic materials leads to significant economic losses, but can also pose serious safety risks. Means of protecting metallic materials against corrosion rely primarily on solutions based on protection by an organic coating, electrochemical protection, and corrosion inhibition.
[0004] Among them, organic coating protection is widely used due to its low cost and ease of use. The coating limits contact between the corrosive environment and the metallic material by providing a barrier.
[0005] However, microscopic defects inevitably exist within the coating, which cannot completely prevent the intrusion of corrosive media. Therefore, the coating only reduces the corrosion rate of the metallic material. Furthermore, the coating ages and may have been improperly applied or undergone degradation, whether intentional or unintentional. All of this results in reduced protective performance and a shortened protection cycle.
[0006] All these phenomena ultimately result in increased porosity or permeability in the coating.
[0007] Also, the evaluation of a physical property of the coating, such as its porosity or permeability, is very useful to check whether it has been correctly applied or degraded, to study how a coating can age and more broadly, for the development of new coatings.
[0008] To date, there are various methods for determining such physical properties of the coating.
[0009] A known solution is to use a porosimeter.
[0010] The approach consists of passing the porosimeter (for example Elcometer 236) in front of a coating to be qualified. The porosimeter is equipped with a high-voltage powered probe (For the Elcometer 236, there are two versions: one at 15kV and the other at 30kV) and by direct current. When the probe passes over a coating defect, a spark occurs and an alarm is triggered. Direct current detectors, like the Elcometer 236, require the porosimeter to be directly connected to the conductive substrate (the metallic material covered by the coating). This technique can be used to test coatings up to 7.5mm thick. It is a technique widely used for inspecting pipelines and protective coatings of metallic materials in general. With this porosimeter, porosity is therefore detected indirectly, by detecting a spark.
[0011] Another solution involves using a pressurization system to adsorb a gas into the coating, and then, with a piston, measuring the quantity of species released when the piston is pulled near the coating. This is, for example, what is proposed in document CN113552058A. This approach, limited to gases, does not work with a species in solution.
[0012] There are also solutions based on measuring the mass gain of the coating related to water penetration into the coating. This is proposed, for example, in the article by Ismail Kada et al., Effect of the organic coating thickness on water uptake measurements by EIS, Progress in organic coatings 197 (2024), 108823, pp. 1-11 (https: / / doi.org / 10.1016 / j.porgcoat.2024.108823).
[0013] Yet another solution is to perform an electrochemical impedance measurement.
[0014] Electrochemical impedance measurement allows the electrical conductivity (which can be related to porosity or permeability) of the coating to be measured by applying a sinusoidal electrochemical signal of variable frequency, based on a coating response that is constant over the measurement period. This is, for example, what is proposed in document CN114609028A.
[0015] Electrochemical impedance measurement can also be used to measure the double-layer capacitance associated with the coating. For example, see the article by Mehrdad Hoseinpoo et al., Simplified approach to assess water uptake in protective organic coatings by parallel plate capacitor method, Materialstoday communications (26), March 2021 (https: / / doi.org / 10.1016 / j.mtcomm.2020.101858).
[0016] Document EP 2 603 801 B1 proposes an electrochemical probe.
[0017] If we take a comprehensive look at the solutions that currently exist, besides the fact that some of them are destructive or inapplicable to certain substrates, it is clear that the accuracy of these solutions proves insufficient.
[0018] One objective of the invention is to offer an improved solution. Summary of the invention
[0019] To achieve the aforementioned objective, the invention proposes a method for determining a physical property of a coating covering a substrate, said method being characterized in that it comprises the following steps: a) place the coating on its substrate in contact with a solution, called the impregnation solution, containing a redox species called the probe species to define a first impregnation zone of the coating; b) leave the substrate in contact with the impregnation solution so that the probe species impregnates the coating over a predefined impregnation time; c) stop putting the coating in contact with the impregnation solution once the impregnation time has been reached; d) put the coating impregnated with the probe species into contact with another solution, called the release solution, to extract the probe species from the coating; (e) concurrently with step (d), perform, by electrochemical means, a measurement of the electrical intensity generated by the quantity of probe species extracted from the coating in the salting-out solution, and f) deduce the desired physical property of the coating, from the measurement carried out in step e).
[0020] The invention therefore consists of exposing the coating to a solution containing a redox species that acts as a probe (impregnation step) during which the probe species penetrates the coating, and then measuring an electrical current generated by the amount of probe species extracted from the coating during a subsequent step (release step). Detection is achieved by placing an electrochemical probe opposite the exposed area and ensuring the release of the species through a change in the composition of the solution to which the coating is exposed.
[0021] The process according to the invention may include at least one of the following additional steps, taken alone or in combination: - the impregnation solution is based on water, N,N-dimethylformamide or acetonitrile. - the probe species is chosen from: Ferrocene, Ferrocenemethanol, K3 FeCN6, K2FeCN6 or Cl3RuNH6. - between step c) and step d), a rinsing step possibly followed by a drying step. - before step f), a step is implemented consisting of measuring the thickness of the coating. - step f) then consists of deducing a relative porosity of the coating, a porosity of the coating and / or a permeability of the coating. - step a) consists of placing the substrate with its coating in the impregnation solution and in this case, step c) consists of removing the substrate with its coating from the impregnation solution. - step a) consisting of placing only part of the substrate with its coating in a vertical position in the impregnation solution, said process includes, between steps b) and c), the following additional steps: A) placing the substrate with its coating deeper in the impregnation solution, at a second predefined depth, the difference in depth between the second depth and the first depth allowing to define a second impregnation zone of the coating; B) leave the substrate in the impregnation solution so that the probe species impregnates the coating over a second predefined impregnation time; C) optionally, repeat steps A) and B) N times, where N is a non-zero natural number, to define other depths, other coating impregnation zones and other predefined impregnation times, step e) then being implemented with a plurality of measurement electrodes, independent of each other and arranged in parallel along the same horizontal direction so as to measure the electrical intensity generated by the amount of probe species released by each of the different impregnation zones; - step a) consists of spraying, for example in the form of a spray, the coating with the impregnation solution and in this case, step c) consists more precisely of stopping spraying the coating with the impregnation solution.
[0022] The invention also provides a device for implementing the method according to the invention, the device comprising: - a first tank intended to receive the impregnation solution containing a redox species known as the probe species, and - a second tank intended to receive the release solution, the second tank housing an electrochemical probe equipped with at least one measuring electrode.
[0023] The device may include at least one of the following features, taken alone or in combination: - another container intended to receive a rinsing solution; - the electrochemical probe includes at least one second measuring electrode, independent of said at least one measuring electrode and arranged in its extension; - the electrochemical probe comprises a plurality of measuring electrodes, independent of each other and arranged in parallel. Brief description of the figures
[0024] Other objects and features of the invention will become clearer in the following description, made with reference to the accompanying figures, in which:
[0025] Fig. 1 is a diagram representing the different stages of a process according to the invention;
[0026] The [Fig.2] is a first example of a device for implementing the process according to the invention;
[0027] Fig. 3 represents, in perspective view, an electrochemical probe that can be used in the device of Fig. 2;
[0028] [Fig.4] represents a means for pressing a coated substrate against the electrochemical probe shown in [Fig.2];
[0029] [Fig.5] represents another means of pressing a coated substrate against the electrochemical probe shown in [Fig.2];
[0030] Fig. 6 represents another electrochemical probe that can be used with the device of Fig. 2;
[0031] The [Fig.7] is a second example of a device for implementing the method according to the invention;
[0032] Fig. 8 represents an example of a measurement carried out with the device of Fig. 2, representing the electrical intensity measured by the electrochemical probe as a function of time. Detailed description of the invention
[0033] Fig. 1 schematically represents the main steps of a process according to the invention.
[0034] The invention relates to a method for determining a physical property of a coating covering a substrate, said method comprising the following steps: a) bringing the coating into contact with a solution, called the impregnation solution, containing a redox species, called the probe species, to define a first impregnation zone of the coating; b) leave the substrate in contact with the impregnation solution so that the probe species impregnates the coating over a predefined impregnation time; c) stop putting the coating in contact with the impregnation solution once the impregnation time has been reached; d) put the coating impregnated with the probe species into contact with another solution, called the release solution, to extract the probe species from the coating; (e) concurrently with step (d), perform, by electrochemical means, a measurement of the electrical intensity generated by the quantity of probe species extracted from the coating in the release solution; and f) deduce the desired physical property of the coating, from the measurement carried out in step e).
[0035] It is understood that the probe species is in solution in the impregnation solution.
[0036] The electrical current measurement performed in step e) is carried out electrochemically. In practice, this can be implemented with an electrochemical probe having one or more electrodes, where, as appropriate, an oxidation or reduction reaction occurs with the probe species (which is a redox species). This allows the quantity of probe species released from the coating, and therefore the quantity of probe species previously impregnated in the coating during step b), to be determined. The sign of the electric current is determined by the nature of the detection process (oxidation or reduction).
[0037] Step a) may consist of spraying the coating, for example by means of a spray, with the impregnation solution. In this case, step c) consists more precisely of stopping the spraying of the coating with the impregnation solution.
[0038] Alternatively, step a) may consist of placing the substrate with its coating in the impregnation solution. In this case, step c) more precisely consists of removing the substrate with its coating from the impregnation solution.
[0039] Step a) can be carried out with different types of probe species (redox), for example, by way of non-limiting: Ferrocene, Ferrocenemethanol, K3FeCN6, K2FeCN6, or Cl3RuNH6. Furthermore, different types of solutions can be used, by way of non-limiting examples: water, N,N-dimethylformamide (DMF) or acetonitrile.
[0040] In a particular case, it may be provided that step a) consists of maintaining the substrate with its coating horizontally in the impregnation solution (not shown).
[0041] In a particular case, step a) may consist of placing only a portion of the substrate with its coating, and maintaining it in a vertical position, in the impregnation solution. In this case, the process may include the following additional steps between steps b) and c): A) place the substrate with its coating deeper in the impregnation solution, at a second predefined depth, the difference in depth between the second depth and the first depth allowing to define a second impregnation zone of the coating; B) leave the substrate in the impregnation solution so that the probe species impregnates the coating over a second predefined impregnation time; C) Optionally, repeat steps A) and B) N times, where N is a non-zero natural number, to define other depths, other coating impregnation zones, and other predefined impregnation times. step e) is then implemented with a plurality of measurement electrodes, independent of each other and arranged in parallel along the same horizontal direction so as to determine the electrical intensity generated by the quantity of probe species released by each of the different impregnation zones.
[0042] Here, we understand that the first impregnation zone has an impregnation time corresponding to the sum of the first impregnation time t1 and the second impregnation time t2, while the second impregnation zone is impregnated only in the shorter time of the second impregnation time t2.
[0043] Step C), which is optional, only generalizes this for additional impregnation areas.
[0044] In this particular context, the electrochemical probe therefore comprises electrodes that are independent of each other and arranged parallel to each other in the same horizontal direction so that each of them is positioned opposite an impregnation zone. A more detailed description is provided below.
[0045] As for step d), one way of proceeding is to place the substrate with its coating impregnated by the probe species in the impregnation solution.
[0046] Advantageously, the process may include, between steps c) and d), a rinsing step, optionally followed by a drying step. Rinsing can be carried out in various ways: spraying with a cleaning solution (water, for example) or soaking in a cleaning solution. As for drying, when implemented, it can be manual drying with absorbent paper, drying by airflow, or other methods.
[0047] It is from the measurement carried out in step e) that one can finally deduce the desired physical property of the coating (step f)), for example its porosity (relative to a reference coating or intrinsic / absolute) or its permeability.
[0048] For example, it is then possible to compare the Pb porosity (relative determination) of two Rb R2 coatings (coating 1 / coating 2) of respective thicknesses e2, noting that (relation RLT1): [Maths 1] _ Ô / î where Qi, Q2 Pi = Qfi represent the charges obtained for the measurements carried out according to the invention for the Rb R2 coatings respectively.
[0049] For each Rb R2 coating, the corresponding charge can be obtained by integrating the electrical current measured using the method according to the invention over the considered release time. Furthermore, the thickness eb e2 of an Rb R2 coating can be measured with a thickness gauge, such as the PCE-CT 26FN offered by PCE Instruments or the Daroplo HW300 Max, both commercially available.
[0050] The relative porosity of the R2 coating can thus be determined with respect to a reference, which would be the Rp coating.
[0051] According to another example, it is possible to determine the intrinsic porosity of a coating (absolute determination, without comparison to another coating). This requires knowing Vu, the volume occupied by a molecule of the probe species (unit: m³). The simplest approach is to consider that at a concentration Co (unit: mol / m³) of the probe species in the impregnation solution, the occupied volume Vu is expressed (RLT2 relation): [Maths 2] y — 1— where N is Avogadro's constant (unit: mol⁻¹) *)•
[0052] From the quantity of charge measured during the release, it is then possible to evaluate the free volume VL per unit area of the coating (or free volume surface density, unit: m) in the coating according to (relation RLT3): [Maths 3] v LAGIâ with: VL~ F^FSn n, the number of electrons exchanged during the measurement carried out by electrochemical means according to the invention (oxidation or reduction) for a probe species molecule, Q, the charge determined over a predefined release time of the electrical intensity measured in step e) F, Faraday's constant (F= 96500 C.mol') S, the electrode surface area that is within the impregnation zone analyzed during release (m2), F co / , the electrode collection factor
[0053] The collection factor depends on the geometric parameters of the geometric configuration used for the measurement, which can be determined from other sources – and is dimensionless. For a given area, the collection factor can be defined as the ratio between the quantity of species detected by the electrode and the quantity of species released by the substrate coating. Protocols for measuring the collection factor of a measuring electrode are available in the literature, for example (https: / / doi.org / 10.1016 / j.jelechem.2012.06.024).
[0054] Using relation RLT2, the reformulated relation RLT3 can then be written: [Maths 4] L IQ C0FcoiFSn
[0055] The porosity PQ of the coating considered, of thickness e (which, as indicated previously, can be known elsewhere with a thickness gauge such as PCE-CT 26FN offered by PCE Instruments) can then be deduced by the relation (relt4 relation): [Maths 5] p _ Ü (unitless). K o - e
[0056] In addition, it is possible to deduce the PM permeability (unit: m2 / s), which is expressed (relation RLT5): [Maths 6] P^ — P^D^ where D is the effective diffusion coefficient of the probe species in the coating (m2 / s).
[0057] The diffusion coefficient (Deff, unit m2 / s) can be calculated using Cottrell's law. Cottrell's equation is valid after a certain analysis time, as can be seen in the concrete example provided below.
[0058] Cottrell's law is expressed in the form (relation RLT6): [Maths 7] f with: I, the electrical intensity measured with the electrochemical measurement according to the invention (A) F cot, the electrode collection factor (unitless) F, Faraday's constant (96500 C.mol1) S, the electrode surface area that is in the impregnation zone analyzed during release (m2) D eff, the diffusion coefficient of the probe species in the coating (m2 / s) Ceff, the concentration of the probe species in the coating (mol.L *) which is equal to Ceff = Po G) where Co is the concentration of the probe species in the impregnation solution t, the time elapsed since the beginning of the release (s) (= release time).
[0059] In practice, the electric current I is therefore the object of the electrochemical measurement carried out within the framework of the invention over the release time t. The other parameters F, F cohS QICeff are known or determinable from other sources. For example, for C, we have C eff = Pq. Co where P o can be determined by the reformulated relation RLT3 and relation RLT4, knowing the thickness e. Furthermore, C 0 is known.
[0060] We can therefore deduce the diffusion coefficient D from relation RLT 6.
[0061] The thickness e of the coating being known from elsewhere (cf. previously, use (using a commercially available thickness gauge), the RLT5 relationship then allows us to obtain the PM permeability of the coating.
[0062] It can be mentioned that numerical simulations using Fick's law in the coating and in the release solution would be a more appropriate model for interpreting the results at short times.
[0063] Figures 2 to 4 represent a first example of a device capable of implementing the process according to the invention.
[0064] In [Fig. 2], the device D comprises a first tank PB for receiving the impregnation solution containing a redox species, referred to as the probe species, a second tank DB for receiving the salting-out solution, and an electrochemical probe SEC equipped with at least one measuring electrode EM opening onto the interior of the second tank DB. This figure also shows a sample ECH of a substrate with its coating, about to be immersed in the impregnation solution, as well as a rinsing tank BR, located between the first tank PB and the second tank DB. On the left, an optional storage tank BS is shown, which allows for the storage of different samples for which the coating permeability needs to be determined.
[0065] In [Fig.3], the electrochemical probe SEC visible in [Fig.2] is shown in a front view showing the EM measuring electrode, looking into the inside of the second DB tank.
[0066] The EM measuring electrode can have varying dimensions depending on the requirements. A large electrode has a larger collection area (and therefore more signal to measure), but also more noise. Conversely, with a small electrode, the noise is reduced but the collection area is smaller. However, there are solutions for reducing noise, regardless of the electrode size.
[0067] As can be seen in [Fig. 3], the SEC electrochemical probe advantageously includes an RBD rim of predefined height H (with reference to the plane of the EM measuring electrode). This provides support for the ECH sample, which can be pressed against the rim, thus controlling the distance between the measuring electrode and the sample coating. Typically, the height H can be between 10 microns and 1 mm, for example, 100 microns.
[0068] The ECH sample can be pressed against the RBD rim of the SEC electrochemical probe in various ways. For example, in [Fig. 4], the clamp P, which holds the sample in a vertical position, is used to also perform lateral positioning. This can be automated, in particular, with control along at least two spatial directions, X and Z. According to another possibility shown in [Fig. 5], an additional PLQ plate equipped with CR spring components is provided. The PLQ plate is housed in the second DB tray, and the CR spring components then press the sample against the RBD rim of the SEC electrochemical probe. Other solutions can, of course, be considered.
[0069] In [Fig.6], another electrochemical probe SEC' is shown comprising several EM1, EM2 measuring electrodes, independent of each other and arranged in parallel, allowing measurements to be taken on different impregnation areas of the coating, having different impregnation times as explained previously.
[0070] In this same [Fig. 6], it is noted that the electrochemical probe SEC' also comprises at least one second measuring electrode EM', independent of said at least one measuring electrode EM and arranged in its extension. When one inserts progressively the sample so as to obtain several impregnation durations during a single detection sequence, this allows to have a doubled measurement.
[0071] It should be noted that an electrochemical SEC probe can be provided with two independent electrodes EM, EM' in line with each other without parallel electrodes EM1, EM2 (case not shown in the attached drawings).
[0072] Fig. 7 represents a second example of a device capable of implementing the process according to the invention.
[0073] In this example, a set of tanks is used, including a first tank PB for receiving the impregnation solution containing a redox species, referred to as the probe species, and a second tank DB for receiving the salting-out solution and housing the electrochemical probe. These tanks are arranged around a robotic arm BRT capable of picking up a substrate with its coating and placing it in the appropriate location. The tanks serve as reservoirs, and the impregnation solution can be applied to the coating by spraying, for example, using a spray gun. This figure also shows rinsing zones 5, 7 (by spraying and soaking), a drying zone 6, and various storage zones 1, 4, 8, 10 for the substrate, for use between the different processing stations. A human-machine interface 11 controls the movements of the robotic arm BRT. Examples
[0074] A sample consisting of a metallic substrate with a commercial anti-corrosion coating (with undercoat, stated corrosion resistance: 10 years) was tested according to the method of the invention, using the device shown schematically in Figures 2 to 4. An impregnation tank contained an impregnation solution with water and K3FeCN6 in solution (concentration Ci) (step a) for impregnation). The impregnation time of the sample was 12 hours (step b)). Then, a rinsing step was carried out, in this case in the form of two successive immersions, in a rinsing tank containing water, for 10 seconds each, followed by drying by manual wiping with absorbent paper.The sample was then placed in the release tank with its release solution (0.1M KC1 electrolytic solution) by placing an electrochemical probe having a single analysis zone (electrode) 100 microns from the surface of the coating, and polarizing it at 0V vs Ag / AgCl.
[0075] The various parameters involved in the reformulated RLT3 relation and the RLT4 relation are as follows: Name n F col Co FS e Value 1 1 100 96500 0.0004 9.105 unit (without) (without) g / LC / mol m2 m Painting
[0076]
[0077]
[0078]
[0079]
[0080]
[0081]
[0082]
[0083]
[0084] It is then necessary to determine the charge Q involved in the reformulated RLT3 relationship, by integrating the electric intensity over the release time. The measurement of electrical intensity as a function of time is provided in [Fig.8]. The test results are presented in a CL curve. For this Cl curve, the signal has been corrected for the current measured before exposure of the coating in the release solution (correction: -29 nA, called baseline). A control measurement was also carried out on curve C2. To obtain this curve In C2, the sample was impregnated for a very short time, namely 2 seconds. The signal was corrected for the current measured before the coating was exposed to the salting solution (correction: -32 nA). Over such short periods, impregnation does not have time to occur. Therefore, what is measured in this case during salting corresponds a priori to an adsorption phenomenon of the probe species within the coating. In any case, by not allowing the K3FeCN6 time to impregnate the coating, only a weak signal is observed. The difference between the Cl (test) and C2 (control) curves therefore comes from the penetration effect of K3FeCN6 (probe species) in the coating. To obtain the charge Q, we integrate the current (C1 curve) over the release time, which here is between the initial time: 405s and the final time: 30000s (the time at which we return to the baseline): we then obtain Q = -2.8 x 10⁴ C. To be more precise, it would be necessary to subtract from this value the charge obtained for the C2 curve by calculating the corresponding current between the same integration limits, but this would change the value marginally and does not add anything to explain the method used. We can then deduce the porosity Podu coating: Po = 2.7.10 4. We can also go further by determining the PM permeability of the same coating. For this purpose, we start with Cottrell's law (relation RLT 6 presented above). Cottrell's law corresponds to curve C3 in Figure 8 (dotted line). As can be seen, this law is valid for long times, namely here t0 = 1500s because it is only from this value that it correctly approximates the curve Cl (test). By implementing a procedure to fit the C3 curve with respect to the curve Cl (trial), we can then express Cottrell's law in the form: [Maths 8] r _ i,210~6. In this case, identification with relation RLT6 allows us to express the diffusion coefficient Dett in the form: [Maths 9] / ) being ~ ( FJFSPfa recalled that CeS = P0.C0 where PQ = 2.7.10 4 as determined previously and Co = 100g / L gives, taking into account the molar mass M(K3FECN6) = 329.24 g / mol, a value of 303.729 mol / m3 which is the unit to be taken into consideration here.
[0085] We deduce Dett = 3.8.107 m2 / s then, by application of relation RLT5, PM = 1.026.10 10 m2 / s.
[0086] It should be noted that the sensitivity of the detection method according to the invention is very high, typically on the order of tens of nanoamperes. This means that the method makes it possible, for example, to detect a release of 3.10 1 °g over a period of 10 s of the probe species for a K3FECN6 release solution in water, with M(K3FECN6) = 329.24 g / mol.
[0087] End of example.
Claims
Demands
1. A method for determining a physical property of a coating covering a substrate, said method being characterized in that it comprises the following steps: a. placing the coating on its substrate in contact with a solution, called the impregnation solution, containing a redox species called the probe species to define a first impregnation zone of the coating; b. leaving the substrate in contact with the impregnation solution so that the probe species impregnates the coating for a predefined impregnation time; c. stopping contact between the coating and the impregnation solution once the impregnation time has been reached; d. placing the coating impregnated by the probe species in contact with another solution, called the salting-out solution, to extract the probe species from the coating; e.concurrently with step d), perform, by electrochemical means, an electrical intensity measurement generated by the quantity of probe species extracted from the coating in the salting solution, and f. deduce the desired physical property of the coating, from the measurement performed in step e).
2. A process according to claim 1, wherein the impregnation solution is based on water, N,N-dimethylformamide (DMF) or acetonitrile.
3. A method according to any one of the preceding claims, wherein the probe species is selected from: Ferrocene, Ferrocenemethanol, K3FeCN6, K2FeCN6 or Cl3RuNH6.
4. A method according to any one of the claims comprising, between step c) and step d), a rinsing step optionally followed by a drying step.
5. A method according to any one of the preceding claims, wherein, before step f), a step is implemented consisting of measuring a thickness of the coating.
6. A method according to the preceding claim, wherein step f) then consists of deducing a relative porosity of the coating, a porosity of the coating and / or a permeability of the coating.
7. A method according to any one of the preceding claims, wherein step a) consists of placing the substrate with its coating in the impregnation solution and in this case, step c) consists of removing the substrate with its coating from the impregnation solution.
8. A method according to the preceding claim, wherein step a) of placing only a portion of the substrate with its coating in a vertical position in the impregnation solution, said method comprises, between steps b) and c), the following additional steps: A. placing the substrate with its coating deeper in the impregnation solution, at a second predefined depth, the difference in depth between the second depth and the first depth defining a second impregnation zone of the coating; B. leaving the substrate in the impregnation solution so that the probe species impregnates the coating for a second predefined impregnation time; C.optionally, repeat steps A) and B) N times, where N is a non-zero natural number, to define other depths, other coating impregnation zones and other predefined impregnation times, step e) then being implemented with a plurality of measurement electrodes, independent of each other and arranged in parallel along the same horizontal direction so as to measure the electrical intensity generated by the amount of probe species released by each of the different impregnation zones.
9. A method according to any one of claims 1 to 6, wherein step a) consists of spraying, for example in the form of a spray, the coating with the impregnation solution and in this case, step c) consists more specifically of stopping spraying the coating with the impregnation solution.
10. Device (D) for implementing the process according to any one of the preceding claims, the device comprising: - a first tank (PB) for receiving the impregnation solution containing a redox species referred to as the probe species, and
11.
12.
13. - a second tank (DB) intended to receive the release solution, the second tank housing an electrochemical probe (SEC) equipped with at least one measuring electrode (EM). Device (D) according to the preceding claim, further comprising another tank (BR) intended to receive a rinsing solution. Device (D) according to any one of claims 10 or 11, wherein the electrochemical probe (SEC) comprises at least one second measuring electrode (EM'), independent of said at least one measuring electrode (EM) and arranged in its extension. Device (D) according to any one of claims 10 to 12, wherein the electrochemical probe (ECP) comprises a plurality of measuring electrodes (EM, EM1, EM2), independent of each other and arranged in parallel.