A coated structure with a monitoring system, a monitoring system, and a method for monitoring the condition of the coated structure.

Abstract

A coated structure with a monitoring system includes a substrate having a substrate surface, a coating coupled to the substrate surface at a substrate interface and extending in the thickness direction to an outer coating surface, a sensor including at least one electrode embedded in the coating, an I / O device configured to generate an input signal in the sensor and read an output signal from the sensor, a data logger configured to record the output signal from the I / O device, and a computer unit configured to use the signal recorded from the data logger. To provide information for improvement related to the condition of the structure or coating, the computer unit is configured to determine at least two separate metrics, each related to a characteristic of the coating or structure.

Description

Technical Field

[0001] This disclosure relates to a coated structure comprising a substrate having a substrate surface and a coating bonded to the substrate surface at a substrate interface and extending in the thickness direction to an outer coating surface.

[0002] The sensor is embedded in the coating, and a data logger is arranged to communicate input and output signals with the electrode structure. Based on the output signal, the computer unit can provide at least two different metrics, each related to the properties of the coating or structure. Background Technology

[0003] For example, various structures made of steel or concrete are coated with coating systems. These coating systems can be used for different purposes, especially to protect against atmospheric degradation (including corrosion, fading, and UV-induced degradation), reduce dirt, improve abrasion resistance, chemical resistance, prevent reflection, or simply provide an aesthetic appearance.

[0004] Ideally, the coating exhibits predefined, desired properties, such as a specific level of protection against the intrusion of air, water, or corrosive substances, thus maintaining the intended condition of the structure. Over time, cracks or coating degradation (i.e., defects or alterations in the coating) reduce the expected performance and may require regular maintenance or repair.

[0005] Coating degradation can be caused by external factors such as temperature, exposure to chemicals including water, and exposure to UV radiation, and can be concentrated in areas such as the colored portions of the coating or the adhesive system. Symptoms of this type of failure include loss of coating integrity or changes in the coating's key properties. Early signs of degradation include the presence of water or other chemicals in the coating.

[0006] Mechanical failures (i.e., the loss of mechanical properties of the coating, such as blistering, cracking, separation, delamination, etc.) can be caused by temperature, impact, interlayer adhesion problems, fatigue conditions, etc.

[0007] For example, if surface preparation is not done properly or if creep corrosion exists on the film, corrosion will occur on the surface of the coated structure.

[0008] For decades, electrochemical impedance spectroscopy (EIS) measurements have been used to measure the dielectric constants of different types of electrolytes. It has been established as a good technique for analyzing coating properties. EIS has been used to investigate the quality of polymer barrier coatings. This is reported in "Electrochemical Impedance of Organic-Coated Steel: Correlation of Impedance Parameters with Long-Term Coating Deterioration," J. Electrochem. Soc. 136, 4, 1989, pp. 979-990.

[0009] Furthermore, in the paper presented by Lee, Chan-Young, Lee, Seung-Kyoung, and Park, Jin-Hwan at the 17th ITS World Congress, titled "Correlation between Surface Deterioration Degree and Electrochemical Impedance Spectroscopy Results for Epoxy Primer-coated Steelfound correlation between the magnitude of the low frequency impedance and long-term deterioration," a correlation was found between the degree of surface deterioration of epoxy primer-coated steel and EIS.

[0010] EIS is a well-established method for analyzing coating degradation and corrosion in standard electrode configurations and portable batteries based on measurements using electrodes located outside the coating. Summary of the Invention

[0011] One objective is to improve the ability to monitor coated structures, particularly the ability to monitor mechanical failures in the form of coating degradation and / or loss of mechanical properties of the coating. Another objective is to provide a structure and system for monitoring corrosion and water on the surface of a coated structure or water within the coated structure.

[0012] When used herein, the term "coated structure" refers to a structure that includes a substrate and a coating system applied to the surface of the substrate. A coated structure with a monitoring system is a coated structure that includes sensors, I / O devices, and computer units.

[0013] For these and other purposes, this disclosure provides, in a first aspect, a coated structure having a monitoring system. The coated structure includes a substrate having a substrate surface, a coating coupled to the substrate surface at a substrate interface, extending along the substrate surface in a longitudinal direction and extending into an outer coating surface in a thickness direction, and a sensor including at least one electrode embedded in the coating.

[0014] I / O devices are configured to generate input signals in sensors and read output signals from sensors.

[0015] The data logger is configured to record output signals from I / O devices, and the computer unit is configured to process the recorded signals from the data logger to determine at least two distinct metrics, each related to a coating or structure.

[0016] The computer unit can specifically process the recorded signal using a first algorithm to provide a first indicator and process the recorded signal using a second algorithm to provide a second indicator.

[0017] In one embodiment, the data logger is comprised of the computer unit itself; in another embodiment, the data logger is comprised of an I / O device; and in one embodiment, it is a separate unit.

[0018] The following non-restrictive list of examples illustrates different ways to implement a monitoring system.

[0019] 1. Since a single monitoring system provides two separate metrics, it can use the same sensor to provide both metrics simultaneously. If the I / O device provides a frequency scan, then the metrics can be provided using the same frequency scan, and they can be defined using the same power supply, the same electronics, etc. Therefore, at least two separate metrics can be defined in a consistent manner. This provides improved opportunities for comparing or combining two metrics.

[0020] 2. At least two separate metrics can express different characteristics, such as water diffusion, degradation, ion presence, corrosion, or cracking, and at least two metrics can be combined to define a condition value that expresses a further condition of the coated structure, which depends on several separate metrics.

[0021] 3. At least two metrics can be derived at different locations within the coating, such as different levels. In this example, the metrics can both relate to the same or different properties. Again, at least two metrics can be combined to define a condition value, for example, that expresses the difference between the metrics at different locations.

[0022] 4. At least one indicator can be formed as a reference indicator that can be used during the curing of the coating.

[0023] 5. At least one indicator can be determined based on a sinusoidal AC signal, and another of at least two indicators can be based on a pulsed DC signal.

[0024] 6. The computer unit can be programmed with a first algorithm applied to the output signal to obtain a first index, and a second algorithm applied to the output signal to obtain a second index.

[0025] When used herein, the properties of a coating or structure are considered to be certain characteristics of the coating or structure, and particularly those that can be observed and expressed by the presence of certain elements, such as water, ions such as chlorides, corrosion or degradation, and especially elements that change over time. In the following text, the term "property" refers only to the presence of one or more of these elements – that is, the property of a coating can be water on or within the coating, it can be the presence of ions, it can be the degradation of the coating, or it can be cracking of the coating. Similarly, the property of a substrate can be corrosion of the substrate or cracking of the substrate. When ions are referred to herein, it can specifically be chloride ions.

[0026] One metric can be defined as a property selected from the group consisting of: water diffusion, degradation, ion presence, cracking of the substrate and / or coating, and corrosion of the substrate. Another metric can be defined as the same property or another property selected from the same group.

[0027] One of the at least two metrics may define a property at one location, and the other of the at least two metrics may define the same property or another property at another location. In one example, the two different locations may be laterally shifted in a direction parallel to the substrate surface or the surface of the outer coating, and in another example, these locations may be shifted relative to each other in a direction perpendicular to the substrate surface or the surface of the outer coating (referred to herein as the thickness direction).

[0028] By using the same sensors, I / O devices, data loggers, and computer units, two separate metrics are determined, established under identical conditions and for the same location. This improves the ability to combine two metrics, for example, by establishing a correlation between the two separate metrics. This correlation can express the coating condition.

[0029] In a specific example, one metric can define moisture content, while another can define coating degradation. If water is detected but coating degradation is not, the expected condition can be considered relatively good, while if both moisture content and coating degradation are detected, the coating condition can be considered much worse.

[0030] In one embodiment, different conditions of the substrate or coating can be anticipated based on the combined value of two separate indicators.

[0031] In particular, for example, embedding electrodes in a coating allows for EIS measurement methods aimed at improving existing systems for determining the condition of a coated structure, especially providing specific knowledge for a particular part of the coated structure.

[0032] When used in this article, the term “monitoring coating degradation” refers to tracking how the coating changes over time.

[0033] For example, the substrate can be an article made of steel, carbon fiber, composite materials, or concrete, such as a part of a ship, pipelines (e.g., in oil or gas installations), pressure vessels, ballast tanks or storage tanks, bridges, wind turbine blades, aircraft, automobiles, or any similar type of structure, for which coating systems are typically used to prevent degradation or improve appearance. Thus, when a monitoring system is used to monitor corrosion, the substrate is a corrosive material such as steel.

[0034] This disclosure may particularly relate to structures that are traditionally difficult and expensive to inspect. It is especially suitable for structures that are hard to access.

[0035] In some embodiments, in addition to being covered by a coating, the substrate is also covered by an insulation layer that is (typically) applied at the final manufacturing point or after on-site assembly. Under-insulation corrosion (CUI) is a well-known problem in many industries, including refining, petrochemical, power, industrial, onshore, and offshore industries. CUI can occur, for example, due to water penetration. CUI most commonly occurs on insulating carbon and low-alloy steel, as well as stainless steel equipment operating at specific temperatures. One form of under-insulation corrosion is sweat corrosion where the pipe operates at temperatures below the atmospheric dew point.

[0036] Because corrosion is hidden beneath the insulation, corrosion-induced corrosion (CUI) often goes undetected until the insulation is removed for inspection or a leak occurs. If left undetected, CUI can lead to serious leaks, equipment failure, extended downtime due to repairs or replacements, and safety and environmental problems.

[0037] Active monitoring of corrosion and / or coating degradation is relatively costly because assessment requires the removal of insulation and possibly also the removal of the coating for visual or other quantitative inspection of the coating or substrate, after which a new protective coating and / or insulation layer must be reapplied. The removal and reapplication of the insulation layer, and possibly the underlying coating, is expensive and provides further possibility of compromising the coating and the protection it provides to the substrate. There may be situations where removing the insulation layer reveals that the coating and substrate are in an acceptable state of mechanical stability. In such cases, the cost of assessing the coating or substrate could be avoided because no remedial action is required. In one embodiment, the coated structure is a coated and insulating substrate. This substrate can form a conduit, i.e., an insulating structure such as a pipe. Corrosion-resistant coatings applied under insulating materials have been disclosed, for example, in US 2020 / 071537 and WO 2018 / 213822.

[0038] In another embodiment, the coated structure is a storage tank or ballast tank of a partially or fully submersible structure (such as a ship or semi-submersible oil drilling platform). When ballasting is required, the interior of the tank is generally susceptible to corrosion due to the presence of water or water vapor (usually seawater). Actively monitored tanks and ballast tanks are costly because they are difficult to access and operations must be stopped during inspections.

[0039] Examples of partially or fully submerged structures include vessels (including, but not limited to, ships, ocean liners, tankers, container ships and all other types of cargo ships, submarines and naval vessels), offshore oil facilities, offshore wind power facilities and subsea pipelines.

[0040] In situations where inspection is difficult and costly, indicators can be extremely useful in providing information without requiring physical access to the structure.

[0041] The substrate surface is the outer surface of the substrate, and it is the surface on which the coating is applied.

[0042] The substrate interface is the interface between the coating system and the substrate. It is often a sensitive area for structure and delamination, where coating separation from the substrate surface can cause rapid substrate degradation. In particular, if the coating itself is intact, degradation at the substrate interface may be difficult to detect.

[0043] When used herein, the term "thickness direction" refers to the direction from the substrate surface to the outer coating surface and perpendicular to the substrate surface. This constitutes the thickness of the coating.

[0044] The coating can consist of any type of paint system, preferably a one- or two-component paint system for steel or concrete, such as a coating system for reducing water diffusion. The latter is well known, for example, for the protection of pipelines or ballast tanks of ships.

[0045] The coating may include a resin matrix material that forms an adhesive, such as an acrylic polymer, alkyd polymer, or epoxy polymer. For example, the coating may include the following adhesives: acrylic, epoxy resin, polyaspartic acid, polyurethane, polysiloxane, alkyd resin, zinc silicate, silicone resin, and polyurea hybrid technology: epoxy / acrylic, epoxy / siloxane, epoxy / zinc silicate.

[0046] The coating may include pigments, for example, to provide color or to form a filler material. Pigments of any color can be considered, such as yellow, orange, red, purple, brown, blue, green, or black, which are part of the official pigment numbering system, for example, described as pigment white xxx (x = 1 to 999), pigment yellow xxx (x = 1 to 999), pigment orange (x = 1 to 999), pigment red xxx (x = 1 to 999), pigment brown (x = 1 to 999), pigment purple (x = 1 to 999), pigment green (x = 1 to 999), pigment blue PB (x = 1 to 999), pigment black (x = 1 to 999), etc.

[0047] Examples of such pigments include: zinc oxide, zinc phosphates and polyphosphates, iron oxide, aluminum phosphates, zinc borate, graphite, carbon black oxide, coated mica, fluorescent pigments, cuprous oxide, aluminum paste pigments (floating and non-floating types), metallic pigments, zinc powder, organic pearlescent pigments, ammonium polyphosphate, colored silica sand, polyacrylic acid / calcium carbonate, azo-based, phthalocyanine and anthraquinone derivatives (organic pigments), and titanium dioxide (titanium oxide (IV)), etc.

[0048] Coatings may include, for example, the following fillers: carbonates, such as calcium carbonate, calcite, dolomite (= calcium carbonate / magnesium carbonate), magnesium silicate / carbonate, and polycarbonate. They may also include mixtures, calcined grades, and surface-treated grades. Silicates, such as aluminum silicate (kaolin, porcelain clay), magnesium silicate (talc, talc / chlorite), potassium aluminum silicate (wollastonite, microcrystalline stone), sodium potassium aluminum silicate (nepheline syenite), calcium silicate (wollastonite), aluminum silicate (bentonite), and layered silicates (mica). Oxides: silicon dioxide (such as quartz, diatomaceous earth), metal oxides (such as calcium oxide, aluminum oxide, iron oxide, and mica iron oxide). Hydroxides / hydrates, such as aluminum hydroxide, aluminum trihydrate, and sulfates: barium sulfate. Other fillers: barium metaborate, silicon carbide, perlite (volcanic glass), glass spheres (solid and hollow), glass sheets, glass and silicate fibers, organic fibers, polyvinylidene chloride acrylonitrile, and polystyrene acrylate.

[0049] It also includes mixtures of the above fillers, as well as natural, synthetic, calcined, or surface-treated grades.

[0050] The coating system may include several layers of coatings, such as a primer, for example, an anti-corrosion primer applied to a substrate surface. For example, the substrate surface may initially be treated by sandblasting. Above one or more primer layers, the coating may include one or more intermediate coatings, such as adhesion-promoting coatings, and / or one or more topcoats. For example, the topcoat may include one or more fouling control surface coating systems, which is particularly useful for marine structures. Electrodes may be arranged between such different coating layers.

[0051] The anti-corrosion primer can be, for example, an epoxy-based anti-corrosion primer, and it can be zinc-containing or zinc-free. Examples of anti-corrosion primers with epoxy-based adhesive systems can be found in WO2014 / 032844.

[0052] Different coating layers can be based on epoxy resin, silicone resin, or polyurethane, and can include, for example, a dirt control surface coating system comprising one or more antifouling coatings, or a silicone resin system, wherein the silicone resin system may comprise similar or different layers of silicone resin coatings. In particular, examples of suitable topcoats for dirt control can be found in patent publication WO 2011 / 076856.

[0053] I / O devices are based on known principles, such as electrochemical impedance spectroscopy (EIS), and use, for example, AC signals to communicate with sensors for input and output signals. For more information on EIS, please refer to A. Amirudin and D. Thieny, “Application of electrochemical impedance spectroscopy to study the degradation of polymer-coated metals”, Progress in Organic Coating, Vol. 26(1): 1-28; “Determination of Coating Deterioration with EIS”, F. Mansfeld, CHTsai, Corrosion, 1991, Vol. 47(12): 958-963; “Re-evaluating Electrochemical Impedance Spectroscopy (EIS) for the Field Inspector's Toolbox: A First Approach”; BJ Merten, A. Skaja, D. Tordonato, and D. Little, U.S. Bureau of Reclamation, Office of Research and Development, Science and Technology Program, Materials Engineering and Research Laboratory (USA), 2014; “Use of Embedded Corrosion Sensors and Sensor Blankets to Detect Paint Degradation”; GDDavis and CMDacres, Corrosion 2003, Paper 3441; “Continuous Monitoring of Atmospheric Corrosion and Coating Degradation” D. Ellicks, F. Friedersdorf, M. Merrill, P. Kramer NACE-2017-8834 March 2017. These and several other publications explain the principles for identifying degradation, for example, by using EIS.

[0054] The coated structure can be a CUI structure, where the coating is in an invisible area and sensors are used to detect coating degradation or underfilm corrosion. I / O devices can be specifically configured for AC signals or pulsed DC signals. In this implementation, the indicators can, for example, involve a combination of two of “water detection,” “coating degradation,” “corrosion,” and / or “cracking.” In particular, detecting the first three mentioned indicators can be advantageous.

[0055] The communication can be achieved via a cable connection between the I / O device and the sensor, or it can be wireless, for example, through sensing, RFID, etc. In particular, the communication can include a cable connection to the sensor via a cable extending into the coating.

[0056] A sensor may include at least two electrodes. The electrodes are spatially separated. The term "spatially separated" means that the electrodes are not in direct conductive contact with each other because they are separated, for example, by air, paint, or other dielectric materials. Even when the paint is conductive, it can still spatially separate the electrodes, especially when the conductivity of the conductive paint differs from the conductivity of the electrodes.

[0057] At least one electrode may be made of a conductive material, such as silver, copper, aluminum, carbon, or materials from the carbon family (including graphene, graphite, etc.), iron, zinc, and any composites thereof. In a preferred embodiment, the conductive material is silver. They may be printed onto the intermediate surface, outer surface of the coating material layers constituting the coating, or onto the substrate surface, or arranged thereon as predefined labels. Thus, the designation of a sensor having one or more electrodes embedded in the coating means that one or more electrodes are located below, in, or on top of the coating, or between layers of the coating, in a manner that allows the characteristics of the structure or coating to be determined from signals in the sensor.

[0058] Methods of applying the sensor may include, for example, stamping, printing, transfer from a carrier material, application by a scraper, or brushing.

[0059] In one embodiment, the electrode is supported by a carrier material. The carrier material herein refers to any kind of membrane that holds the electrode in place at least until it is supported by the coated substrate, i.e., until the coated structure is formed. The carrier material can allow the electrode to be predefined for application to the substrate. In a preferred embodiment, the carrier material is removed after the electrode is applied, thereby allowing water and ions to flow freely around the electrode.

[0060] In one embodiment, the electrodes may be brushed or printed with liquid conductive ink, and therefore not supported by a carrier material.

[0061] By using at least one single electrode, this indicator can relate to cracking. However, in particular, the sensor can have at least two electrodes, thereby enabling capacitance measurements and the use of EIS, for example, for detecting water and degradation. Thus, in the case of two electrodes, the indicator can particularly relate to water and degradation.

[0062] Electrodes can have different shapes, sizes, or configurations. In one embodiment, an electrode includes at least one elongated electrode; in another embodiment, an electrode has a curved shape; and in yet another embodiment, at least one electrode forms a comb pattern. In one embodiment, two electrodes form a comb pattern, with the fingers of the pattern on one electrode interlacing between the fingers of the pattern on the other electrode.

[0063] Computer units use output signals to determine at least two parameters. Input and output signals can specifically be AC ​​signals.

[0064] When used herein, the term "index" is a measure of the properties of a coated structure. Examples of indices may be numerical values ​​on a scale representing properties such as water diffusion, degradation of the coating or coated structure, and the presence of ions, cracking, or corrosion. These properties are mentioned throughout this description as examples of properties of the coated structure, but other properties may be relevant, such as delamination. While an index is a measure of such a property, it can be dependent on certain conditions. For example, the input and output signals may be AC ​​signals, and a computer unit may determine capacitance based on impedance and the phase shift between the input and output signals. Capacitance is significant for the moisture content in or at the coated structure and can be one of two indices. The relationship between capacitance and moisture content depends on various other factors, such as temperature and humidity. Thus, while the index is a measure of a property, it can be dependent on other factors.

[0065] The computer unit can be specifically configured to determine at least one of two parameters via EIS. This can be achieved using an AC signal with a sinusoidal shape or a signal with a waveform or triangular shape. Alternatively, at least one of the two parameters can be found by using a DC pulse signal. In that case, the delay between the input and output signals is determined. The delay is important for capacitance, which in turn is important for the presence of water or other chemicals, or for temperature or humidity. The process for detecting water will be described in detail later, and includes calculating frequency-dependent impedance in addition to measuring phase shift.

[0066] The resistance in a DC pulse signal can be determined from the amplitude and is of great significance for cracking or material changes (including degradation).

[0067] In one embodiment, the sensor may include at least three electrodes, and the computer unit may be configured to determine one of two metrics via EIS. This is accomplished using a first set of two of the three electrodes, and the other of the two metrics is determined via EIS using a second set of at least two of the three electrodes.

[0068] The input signal can define a first electric field between a first set of electrodes and a second electric field between a second set of electrodes. The first and second electric fields can define field curves with different dimensions or shapes. This can be used as referred to herein as the "detection volume." The detection volume refers to the measurement field, for example, and can be used for:

[0069] • Determine the water content in the coating. This can be achieved by ensuring that the spatial distance between the electrodes is less than the distance from the electrode to the outer coating surface and less than the distance from the electrode to the substrate interface.

[0070] • Determine film corrosion: This can be obtained by the spatial distance between electrodes being less than the distance from the electrode to the surface of the outer coating and greater than the distance from the electrode to the substrate interface.

[0071] • Determine the water formation in the top coating layer: This can be achieved by ensuring that the spatial distance between the electrodes is greater than the distance from the electrode to the outer coating layer and less than the distance from the electrode to the substrate interface.

[0072] • Crack identification. This can specifically be a single electrode with a straight or elongated shape, where the resistance changes when the electrode fails. It can also be a single electrode with multiple lines, for example, parallel lines that also allow for determining crack size. If half of the lines are damaged, then the length of the crack will be roughly equivalent to half the length of the line pattern. Underfilm corrosion can be detected, and faults in sensors can be detected, for example, if one of the electrodes fails. The latter can be used to define whether cracking exists in the coating at the sensor location. This is done by measuring the conductivity between the two edges of the electrode. If the conductivity is zero, then the electrode is damaged, and this could be due to cracking in the coating.

[0073] In one embodiment, the field curve for a first electric field of a specific field strength extends to the surface of the outer coating, while the field curve for a second electric field of the same specific field strength does not extend to the surface of the outer coating.

[0074] For example, the specific field strength of the field curves comparing the first and second fields could be a 95% field strength curve or a 99% field strength curve.

[0075] In one embodiment, the field curve for a first electric field of a specific field strength can be extended to the substrate interface, while the field curve for a second electric field of the same field strength may not be extended to the substrate interface.

[0076] In one embodiment of this type, the field curve for a first electric field of a specific field strength extends to the substrate interface and the surface of the outer coating, while the field curve for a second electric field of the same field strength does not extend to the substrate interface and the surface of the outer coating.

[0077] The computer unit can be configured, for example, to simultaneously use electrical signals present between electrodes in a first set of electrodes and electrical signals present between electrodes in a second set of electrodes, and to determine at least an index.

[0078] In the above examples of different sizes of field curves, the control structure can therefore be configured to generate information related to the position of the outer coating surface, the substrate surface, the substrate interface, and / or within the coating simultaneously and by using signals from different sets of electrodes at the same time.

[0079] The distance between the electrodes in the first set of electrodes may differ from the distance between the electrodes in the second set of electrodes. Alternatively or in combination, at least one characteristic of the electrodes in the first set of electrodes (such as one of the size, shape, construction, and / or material of the electrodes in the first set of electrodes) may differ from the material of the electrodes in the second set of electrodes. The different distances, sizes, shapes, or materials mentioned above can produce different field curves for the same electric field intensity.

[0080] In one embodiment, the first set includes a first electrode and a second electrode, and the second set includes a third electrode and a fourth electrode. In an alternative embodiment, the first set includes a first electrode and a second electrode, and the second set includes a second electrode and a third electrode.

[0081] Two, three, four, five or more sets can be defined, each set consisting of two electrodes.

[0082] Electrodes can be located at different depths within the coating. In one embodiment, the electrodes of a first set of electrodes can be located at different depths in the thickness direction relative to the electrodes of a second set of electrodes. This will also create field profiles with different origins, thus providing the ability to characterize different regions of the structure or coating.

[0083] One of the at least two metrics can be obtained from an electrode at one depth within the coating, and the other of the at least two metrics can be obtained from an electrode at another depth within the coating. In this embodiment, the metrics can be used to derive a combined value based on at least two metrics obtained from electrodes at different depths.

[0084] In one example, the first of the two metrics is derived from an electrode near the outer surface of the coating, for example, 150 μm from the outer surface, and the second of at least two metrics is derived from an electrode not too close to the outer surface of the coating, for example, 300 μm from the outer surface. In this case, both metrics may relate to water, or they may both relate to one of the other properties mentioned above (e.g., degradation, corrosion, or cracking). If the first metric indicates a higher water content than the second metric, then the difference between the metrics can indicate the rate at which water penetrates the coating. In this case, the combined value can indicate the penetration rate. For example, separate metrics can be provided for 2, 3, 4, 5, or more different depths in the coating.

[0085] In one embodiment, one or more electrodes are covered with an insulating material (such as a polymer or ceramic material) or any material with a lower conductivity than the electrodes. This can alter the ability of the field curve to propagate, thus creating different field curves for the same electric field strength. The insulating material can be applied to or near one or more electrodes of varying thickness, thereby controlling and exciting different field curves from the electrodes.

[0086] In one embodiment, the computer unit is configured to measure the conductivity or resistance between the edges of one or more electrodes. This can reveal whether the electrodes are still functioning and can predict cracking of the electrodes or structures and coatings.

[0087] For example, indicators for cracking can be identified, as expressed, for example, in the article “Multi-Channel Electrical Impedance-Based Crack Localization of Fiber-Reinforced Cementitious Composites under Bending Conditions” by Man-Sung Kang, Hanju Lee, Hong Jae Yim, Yun-Kyu An, and Dong Joo Kim, published in Applied Sciences MDPI in 2018.

[0088] The computer unit can be configured to use recorded signals to define at least two separate metrics simultaneously.

[0089] The coating may include different coating layers, such as a first coating layer and a second coating layer. Each layer includes opposing inner and outer surfaces, with the inner surfaces bonded at the coating interface. For example, the outer surface of the first layer may be bonded to the substrate at the substrate interface.

[0090] In this embodiment, at least one of the at least two electrodes of the sensor may be located in the coating interface.

[0091] The first layer can have a first thickness and the second layer can have a second thickness different from the first thickness.

[0092] In one embodiment, one of the at least two metrics relates to the substrate interface, while the other of the at least two metrics relates to the outer coating surface.

[0093] At least one of the two metrics may involve the substrate interface, and at least the other of the two metrics may involve the outer coating surface.

[0094] At least one of the two indicators may relate to cracking within the coating system, or the barrier properties of the system, or the water permeability within the coating, or undercoating corrosion at the substrate surface, or water formation, curing degree, or film formation on the surface of the outer coating, wherein film formation includes curing or evaporation.

[0095] The computer unit can be configured to determine an indicator related to cracking in the coated structure using the resistance in one of at least two electrodes of the sensor. This can be done by determining the resistance of one of the electrodes shortly after the coated structure is fabricated and storing that resistance as a reference resistance. Throughout the lifespan of the coated structure, the resistance of that electrode can be compared to the reference resistance, and if the difference exceeds a threshold, it can be considered an indication of cracking or other issues in the coating.

[0096] The computer unit can be configured to receive configuration data recorded during coating curing and generate a reference pattern based on the configuration data. The computer unit can also be configured to use the reference pattern to determine the degradation level of the coating. Specifically, the data recorded during curing can be recorded within the first 10-20 hours after coating application. Within this timeframe, coating polymerization can occur, and the signals obtained are comparable to the corresponding signals obtained during degradation. Therefore, the data recorded during curing can be used as a reference, and when a similar signal is observed later, it can be considered an indication of degradation. Thus, the computer unit can be configured to compare the reference pattern with the subsequently obtained signal, i.e., to compare the reference pattern with the recorded output data.

[0097] The output from the electrodes is typically temperature-dependent. In particular, capacitance measurements depend on temperature, and may also depend on humidity, etc., and resistance, impedance, and inductance measurements also depend on temperature. Therefore, the computer unit can communicate with a temperature sensor configured to determine the temperature of the coating. The temperature can be stored and used for correlation and correction of the output signal.

[0098] In one example, temperature is used to define at what temperature the coating structure is indices for curing, degradation, moisture content, or other properties.

[0099] In one example, the reference pattern mentioned above is adjusted based on temperature before being compared with a specific signal obtained later.

[0100] The computer unit can be configured to provide one of at least two metrics that relate to a characteristic selected from the group consisting of: water diffusion, degradation, ion presence, cracking of the substrate and / or coating, and corrosion of the substrate, and wherein the computer unit is configured to provide another of the at least two metrics that relate to the same characteristic or another characteristic selected from the same group. For this purpose, the methods described above for determining metrics representing such characteristics can be programmed into the computer unit.

[0101] Specifically, the computer unit can be configured to determine metrics based on frequency-scanned input signals. I / O devices can therefore be configured to generate input signals in the form of frequency scans, and the computer unit can be configured to use recorded signals from a data logger and determine at least two separate metrics based on the same frequency scan. This allows for enhanced options for comparing two metrics or for combining two metrics to provide values ​​(e.g., expected conditional values ​​as mentioned earlier). Because the metrics are derived from the same frequency scan, there are no discrepancies due to tolerances in the frequency scan.

[0102] Frequency scanning means providing an input signal at a frequency that varies within a specific bandwidth (such as 0.1 to 100,000 Hz).

[0103] In a second aspect, this disclosure provides a monitoring system for integration into a coated structure, the coated structure comprising a structure having a substrate surface, a coating coupled to the substrate surface at a substrate interface and extending in the thickness direction to an outer coating surface, and a sensor including at least one electrode embedded in the coating.

[0104] The monitoring system includes:

[0105] -I / O devices are configured to generate input AC signals in sensors and read output AC signals from sensors.

[0106] - A data logger, configured to record output AC signals from I / O devices, and

[0107] - A computer unit is configured to utilize signals recorded from a data logger and determine at least two separate metrics, each related to the properties of the coating or structure.

[0108] In a third aspect, this disclosure provides a method for monitoring the condition of a coated structure, the coated structure comprising a structure having a substrate surface, a coating coupled to the substrate surface at a substrate interface and extending in the thickness direction to an outer coating surface, and a sensor including at least one electrode embedded in the coating.

[0109] The method includes the following steps:

[0110] - Generate input signals in the sensor and read output signals from the sensor.

[0111] - Use a computer unit to determine at least two separate metrics based on the output signal, each metric being related to the properties of the coating.

[0112] In a fourth aspect, this disclosure provides the use of a sensor comprising at least one electrode embedded in a coating of a coated structure for obtaining at least two metrics, each related to a characteristic of the coating, by means of:

[0113] - Generate input signals in the sensor and read output signals from the sensor, and

[0114] - Apply the first algorithm to the output signal to obtain the first index, and apply the second algorithm to the output signal to obtain the second index.

[0115] Any feature mentioned in relation to the first aspect of this disclosure may also be applied to the monitoring system of the second aspect of this disclosure and the method of the third aspect of this disclosure. Attached Figure Description

[0116] The embodiments will now be described in further detail with reference to the accompanying drawings, in which:

[0117] Figure 1a -d illustrates the structure of a sensor with a coating and electrodes embedded in the coating;

[0118] Figure 2 An embodiment with four electrodes arranged in two pairs and a comb-like pattern is illustrated;

[0119] Figure 3 The diagram illustrates three electrodes that form two pairs of electrodes;

[0120] Figure 4-5 The illustration shows two sensors with different numbers of electrodes;

[0121] Figure 6 The diagram illustrates the detection volume;

[0122] Figure 7 The illustration shows two electrodes with a comb-like pattern of interlaced fingers;

[0123] Figure 8The diagram illustrates the ratio between the spacing ratio and the current flowing through the electrodes;

[0124] Figure 9 The diagram illustrates the output signal;

[0125] Figure 10 The illustration shows four different sensors, each of which includes two electrodes;

[0126] Figure 11 The diagram illustrates five different sensors, each consisting of one electrode;

[0127] Figure 12 The illustration shows an electrode pattern with a zigzag shape;

[0128] Figure 13 and 14 The diagram illustrates a two-electrode pattern suitable for degradation, water testing, corrosion detection, and cracking detection; and

[0129] Figure 15-19 The experiment and its results are presented. Detailed Implementation

[0130] It should be understood that while the detailed description and specific examples indicate embodiments, they are given by way of illustration only, as various changes and modifications based on this detailed description will become clear to those skilled in the art within the spirit and scope of this disclosure.

[0131] Figure 1a The diagram illustrates a coated structure 1 with monitoring capabilities. The coated structure includes a substrate 2, for example, made of steel. The substrate has a substrate surface 3 protected by a coating 4. The coating is bonded to the substrate surface at a substrate interface 5, and the coating extends in the thickness direction indicated by arrow 6, thereby forming the thickness of the coating. This coating forms an outer coating surface 7 facing away from the substrate 2.

[0132] A sensor comprising four electrodes 8, 9, 10, and 11 is embedded in the coating. Two of the four electrodes, 8 and 9, constitute a first set of electrodes, and the other two electrodes, 10 and 11, constitute a second set of electrodes.

[0133] The potentiostat 28 communicates with the sensor by introducing a signal into the sensor and reading the output signal from the sensor. The potentiostat constitutes an I / O device as understood in this context. The I / O device can be wired to the electrodes of the sensor, or, as shown in Figure 1, it can communicate wirelessly with the electrodes. Wireless communication enables the electrodes to be fully embedded in the coating, thereby providing a more robust system.

[0134] I / O devices can specifically provide frequency-scanned input signals, for example, in the frequency range of 0.1–100000 Hz.

[0135] The I / O device communicates electrical signals with the computer unit 12, and the computer unit is configured to derive the condition of the coating, the condition of the substrate, or the condition of the substrate interface from the electrical signals from the sensor.

[0136] Due to the two categories (i.e., the first and second sets of electrodes), the computer unit can determine at least two distinct properties of the coated structure, referred to herein as the first and second indices or other indices.

[0137] Figure 1a The illustration shows an embodiment where electrodes 8, 9, 10, and 11 are located side-by-side at the same depth within the coating.

[0138] Figure 1b The illustration shows an embodiment in which electrodes 8, 9, 8', and 9' are positioned above each other at different depths within the coating.

[0139] Figure 1c The illustration shows an embodiment where electrodes 8, 9, 10, and 11 are displaced relative to each other and located at different depths within the coating.

[0140] Figure 1d The illustration shows an embodiment where electrodes 8, 9, 8', and 9' are positioned above each other at different depths within the coating, and also includes electrodes 10 and 11 that are displaced relative to each of the other electrodes. In the illustrated embodiment, electrodes 10 and 11 are located at the same level as electrodes 8' and 9', but they could also be located at a different level than the other electrodes within the coating.

[0141] Figure 2 The embodiments are illustrated in more detail. The first set of electrodes 21 defines the first and second electrodes 22, 23 as interleaved conductors, and the second set of electrodes 24 defines the third and fourth electrodes 25, 26 as interleaved conductors.

[0142] Each pattern is connected via bus structure 27 to a local I / O device 28 for power supply and signal transmission. This device includes a CPU unit and is configured to provide input signals with different frequencies.

[0143] The local I / O device 28 powers the pattern and transmits the response signal received from the pattern via the bus-wire 27. For example, the local I / O device 28 can be configured to output an AC signal with a frequency of 10 μHz to 1 MHz, a current range of 100 pA to 10 mA, and a potential range of ±5 mV or ±10 V.

[0144] Local I / O device 28 can communicate response signals or signals derived from response signals to computer unit 12, and it can include internal storage to allow intermittent communication with computer unit 12. By including internal storage, the local I / O device also defines a data logger that can record data from sensors. Data recording can also be performed in a separate computer unit between local I / O device 28 and computer unit 12. Local I / O device 28 can be, for example, a PalmSens4 from PalmSens Corporation. TM It consists of a potentiostat / galvanometer CS350 from Corrtest Instruments, or a similar commercially available potentiostat, galvanometer, or similar impedance analysis device.

[0145] In addition, it can include a multiplexer to share the signal among multiple sets of electrodes. Another available potentiostat is the Ivium, PocketSTAT2 from Ivium Technologies.

[0146] Local I / O devices can be powered independently, for example, by solar panels or batteries. In one embodiment, the local I / O devices are very thin and are disposed on, or even under or within, the coating.

[0147] The computer unit 12 is configured to also process response signals, to present results based on the response signals, or to collect and optionally compare and / or present response signals from a plurality of local I / O devices 28, each local I / O device 28 being connected to two or more patterns via bus-wiring. The computer unit 12 also includes a data logger for collecting the collected data.

[0148] Figure 3 The diagram schematically illustrates one embodiment of the electrode. In this embodiment, the substrate 31 has a substrate surface 32 covered by a coating 33. The coating is made of a first layer 34 and a second layer 35 of coating. The two layers have different thicknesses. The electrode structure is arranged between the layers and consists of a first electrode 36, a second / third electrode 37, and a fourth electrode 38. The second and third electrodes are the same electrode, and a total of three electrodes form a set of two electrodes.

[0149] The first electrical signal between the first electrode 36 and the second / third electrode 37 defines the first electric field 39, and the second electrical signal between the second / third electrode 37 and the fourth electrode 38 defines the second electric field 40.

[0150] For a given electric field strength, two electric fields will have different field curves. For example... Figure 3As schematically shown, field curve 39 extends to the surface of the outer coating, while field curve 40 extends to the surface of the substrate and covers the substrate interface between the substrate and the coating.

[0151] Figure 4 The electrode structure is illustrated schematically.

[0152] Figure 5 The diagram illustrates an alternative electrode configuration where a first set includes a first electrode and a second electrode, and a second set includes a third electrode and a fourth electrode. In this configuration, the two electrode sets are defined by using four electrodes.

[0153] Figure 6 The diagram illustrates the electric field volume, where 61 is the distance between the electrodes, and the curves show different percentages of current flowing within the volume. When an AC potential is applied between the two electrodes, a current is induced, thus creating an electric field. The electric field provides the quantity detected. If the focus is on coating degradation, then the magnetic field needs to be confined within the coating. The electric field volume percentage indicates the magnitude of the current below the curve.

[0154] Figure 7 The set of electrodes includes a first electrode 71 and a second electrode 72 forming fingers, the second electrode 72 being formed between the fingers of the first electrode.

[0155] Figure 8 The spacing ratio (W) on the horizontal axis is illustrated as a curve. sp The relationship between / L), where W sp is the spacing between adjacent electrodes, and L is the distance from the center of one electrode to the center of the adjacent electrode. On the vertical axis, the current through the layer is represented by the thickness indicated on each of the three graphs. The top graph shows a coating thickness of 0.8 times the distance L between the electrodes, the middle graph shows a coating thickness of 0.4 times the distance L between the electrodes, and the bottom graph shows a coating thickness of 0.2 times the distance L between the electrodes.

[0156] Figure 9 The output signal is illustrated, with the absolute impedance Zabs (ohms) plotted over a total frequency range from 1E5 Hz to 0.1 Hz. Different curves represent measurements taken at different times. Over time, the curves shift towards lower Zabs values ​​in the lower frequency range.

[0157] Figure 10The illustration shows four different sensors, each consisting of two electrodes, i.e., a two-electrode pattern. This type of sensor is suitable for detecting coating degradation, corrosion, and water detection, for example, via EIS. Sensors a and b form a comb-like pattern with interlaced fingers. The number and spacing of the fingers can vary. Sensor c forms rectangular parallel lines. The spacing between the lines can vary. Sensor d forms a plate-like electrode arranged at varying distances. The plate can be applied between different layers of coating, for example, between different coating layers. The plate can be applied with or without an insulating layer between them.

[0158] Figure 11 The illustration shows five different sensors, each consisting of a single electrode, i.e., a one-electrode pattern. This one-electrode pattern is suitable for detecting cracks.

[0159] Sensors b, d, and e are 1-dimensional long sensors. For example, they can range from a few centimeters to several meters. They are suitable for crack detection, where cracks in the coating damage the electrodes, causing a significant increase in resistance from one end of the electrode to the other.

[0160] Sensors a and c are two-dimensional sensors that include a single electrode and are suitable for area mapping, for example, from 0.1 square meters to several square meters.

[0161] A single-electrode pattern sensor can be combined with a two-electrode pattern to achieve combined sensing of separate indicators.

[0162] Figure 12 A specific embodiment of an electrode pattern having a zigzag shape is illustrated.

[0163] Figure 13 and 14 The diagram illustrates a two-electrode pattern suitable for degradation, water detection, corrosion detection, and crack detection, all within a single sensor. Utilizing the three electrode connection points, combined impedance and resistance are possible, formed by only two separate lines connecting the three electrodes.

[0164] Experimental Section

[0165] Preparation of the coated structure. Three different types of substrates were used: hot-rolled soft 235J steel sheet, hot-rolled soft 235J steel pre-corroded sheet, and acrylic sheet, all with dimensions of 75x150x3mm. The steel sheet was sandblasted with iron shot (G070acc.ISO 11124) to achieve Sa2. 1 / 2 Cleanliness (G) (ISO 8503-1). Pre-corrosion is performed by exposing the panel to 95% relative humidity at 30°C for 48 hours to produce a uniform flash rust layer on the substrate surface.

[0166] The substrate was coated with a four-component two-part bisphenol A-based epoxy coating (Hempadur mastic 45880), comprising a substrate (epoxy resin component) and a curing agent (amine component) mixed at a ratio of 1:3 v / v. Each layer was 150 micrometers thick and applied to the substrate using airless spraying. The total dry film thickness (dft) of the coating was 600 micrometers. The first three layers were allowed to cure for one week, while the last and fourth layers were allowed to cure for two weeks. A total of 144 coated structures were prepared.

[0167] Fabrication of coated structures with a monitoring system. Each of the 144 coated structures embedded a dual-electrode sensor. Three sensor designs were placed at different locations between the four coating layers (one sensor per coated structure): 150 μm from the substrate surface (inner layer), 300 μm from the substrate surface (middle layer), and 450 μm from the substrate surface (outer layer). These three designs have a comb-like structure with different finger spacings: 300 μm, 500 μm, and 2500 μm. The sensors were made from ink composed of silver nanoparticles and embedded between the coating layers using two different methods. The first method involved imprinting silver-containing ink onto the coating layer followed by thermal curing. The second method involved transferring a conductive pre-printed sensor from the foil to the coating layer. Both methods yielded well-functioning sensors with low sheet resistance.

[0168] Table 1 below indicates the matrix of the fabricated coated structures containing sensors. Experiments were conducted using three different substrate surfaces and three different sensor designs. Sensors were applied at three different depths using two different application techniques. All combinations were completed, for example, combining steel as the substrate surface with all three sensor designs, sensor locations, and sensor application techniques. For each parameter combination, at least three copies were fabricated.

[0169] Table 1

[0170]

[0171] The I / O equipment includes an "Ivium CompactStat.h" potentiostat and an "Ivium HiMUX.XR" multiplexer that enable sequential measurements on 64 channels, as well as a computer. Each sensor is connected to one channel of the multiplexer via a cable that connects to each of the sensor's two electrodes, such as... Figure 15 As shown in the diagram, three I / O devices are used, two of which include eight multiplexers and the third contains two multiplexers. Figure 15The diagram illustrates a substrate 151, a coating 152, a sensor including two electrodes 153 and 154, an eight-channel multiplexer 155, an eight-channel coupler 156, a potentiostat 157, and a computer 158.

[0172] Test and Experiment Results. The coated structures with embedded sensors were placed in a salt spray chamber and exposed to 5% NaCl mist at 35°C for 14 weeks. Electrochemical impedance spectroscopy (EIS) measurements at 50 mV were performed every 5 hours on each coated structure. The signal amplitude was 50 mV and 61 frequencies were scanned, from 0.1 Hz to 1E5 Hz. Figure 9 An example of a typical spectrum obtained for all plates at the start of the experiment is shown. The EIS signal will respond to varying environmental conditions applied throughout the system, including the embedded electrodes in the coating.

[0173] When water penetrates the coating, it initiates a series of subsequent processes. First, the accumulation of water within the pores and pockets of the coating causes the pore size to increase with water absorption, a type of degradation. Second, the overall electrical properties of the material change through variations in the material's conductivity and dielectric constant, measured as changes in capacitance and resistance in the EIS signal response. Corrosive ions diffusing into the coating over time can further enhance this response.

[0174] exist Figure 16 and 17 In the figure, the imaginary part of the impedance at high frequency (100kHz) is plotted relative to the elapsed experimental time. That is, the horizontal axis shows the elapsed time in hours, and the vertical axis shows lm (ohm)rel [%].

[0175] Figure 16 and 17 This is a graph plotted for sensors located at distances of 150 micrometers (inner layer, "o"), 300 micrometers (middle layer, "x"), and 450 micrometers (outer layer, "*") from the substrate surface. This behavior represents all coated structures. For structures where the sensor is located in the inner and middle layers, an initial increase in the imaginary part occurs within the first 150 hours. When the electrode is located in the outer layer, this increase extends up to 300 hours. After this, the imaginary part plateaus, followed by a second increase after 600 hours, cf, as indicated by arrow 174, when the electrode is embedded in the middle layer.

[0176] The initial increase in the imaginary part is related to water absorption. When the electrode is located in the inner and middle layers, water begins to diffuse through the coating and saturates after approximately 200 hours. For this type of coating and under the experimental conditions outlined, this applies to electrodes at distances of 150 μm and 300 μm from the substrate. When the electrode is located in the outer layer, at a distance of 450 μm from the substrate in our case, the secondary processes involving degradation and ion transport cannot be separated from the water absorption signal, resulting in a further increase in the imaginary part, where the signal time response is extended to up to 350 hours. To distinguish between the two initial cases (171-water absorption or 172-water absorption + degradation), the entire complex impedance over the total frequency range should be evaluated:

[0177] 1- If the increase is purely due to water absorption in the coating, then the overall EIS signal flattens out at lower frequencies.

[0178] 2- If the increase is caused by a combination of water absorption and degradation as well as ion transport, then the EIS complex impedance curve will completely change shape.

[0179] Following this initial increase, a plateau is reached regardless of whether the coating has undergone any kind of degradation and ion transport processes. This corresponds to the case where the coating layer is completely saturated with water. A second increase in the imaginary component is observed approximately 600 hours later, when the electrode is in the intermediate layer. This corresponds to the case where degradation and ion transport processes begin to occur, and in this particular case, it is prolonged by approximately 1500 hours.

[0180] In summary, in this specific example, a single sensor has been used to evaluate more than one property of the coating: water diffusion, degradation, and ion presence.

[0181] Electrodes located in the outer layer of the coated structure (450 micrometers in this example) are also sensitive to humidity and liquid water on the surface of the coated structure. For three different sensor designs, detection occurs immediately, such as... Figure 18 As shown, the EIS spectrum of the coated structure where the sensor is located in the outer layer is plotted. Figure 18 In the graph, the horizontal axis represents 10log(frequency) / Hz, while the vertical axis represents 10log(Z) / ohm.

[0182] Measurements were performed when the structure was dry and after approximately 3 ml of liquid water was added to the top of the coated structure surface, denoted as "dry" and "wet," respectively. The response to liquid water was measured for three different sensor designs: a comb structure with a finger spacing of 300 micrometers (△ "dry," ◇ "wet"), a comb structure with a finger spacing of 500 micrometers (+ "dry," ◆ "wet"), and a comb structure with a finger spacing of 2500 micrometers (■ "dry," ▲ "wet"). For all three sensor designs, the modulus of impedance at high frequencies, associated with the coating capacitance, decreased when water was on the surface of the coated structure (denoted as "wet"), demonstrating that all three sensor designs are sensitive to liquid water. This decrease was similar for the comb structures with finger spacings of 300 micrometers and 500 micrometers (4000 ohms), while it was greater for the comb structure with a finger spacing of 2500 micrometers (10000 ohms). This indicates that the last design is more sensitive to liquid water.

[0183] The same experiment was performed on the coated structure with the sensor embedded in the intermediate layer. In this case, the EIS spectrum remained constant, independent of the presence of liquid water. Humidity detection depended on the sensor's position within the coated structure.

[0184] General formula for indicators

[0185] A general metric is defined to provide comparable insights into how coating properties change over their lifespan when exposed to different environmental conditions (such as varying temperature T, humidity RH, pressure p, etc.). In addition to environmental conditions, the complex impedance is measured at time t and frequency f. Measurements across the entire frequency domain under fixed environmental conditions can be correlated with equivalent circuit components (most commonly resistors and capacitors), for example, through fitting. Therefore, when evaluating system changes, we directly look at the changes in the values ​​of the equivalent circuit components measured over different time periods, as well as the complex impedance, while also considering environmental variations to make the measurements comparable; i.e., A(t,f,T,RH,p,…) where A is one of the system characteristics just mentioned: complex impedance Z, equivalent circuit components, such as resistor R or capacitor C, or other circuit components. However, it also includes the real and imaginary parts of the complex impedance, i.e., and And the modulus of complex impedance.

[0186] Then, the index is a mapping of characteristic changes measured at different times under comparable adjusted environmental conditions, designated as A. n We have,

[0187] I(A)=g(A1,A2,…,A N (G1)

[0188] Where g is a function describing the change, for two indicators, it can look like this:

[0189]

[0190] Of course, g can be defined more "strongly" with multiple inputs to provide greater accuracy for predictive algorithms describing change. Sometimes, for practical reasons, the notation convention is changed to express reduction as a positive number, and the ratio can be expressed as a percentage. Furthermore, the time derivative of g can be calculated to assess the rate of change of the system.

[0191] The above index structure is general, but many different indices arise depending on the situation, and these can be distinguished by a series of indicators. In these cases, specific indicators must be evaluated during the analysis of coating material properties to calculate the appropriate index, and they may be accompanied by a subset of supporting equations that must be satisfied. We now present these indicators, but first, we will explain the order of events. 1) Water detection is sometimes distinguished as water on the surface and water absorption, 2) Coating degradation and ion transport, 3) Corrosion. While this is generally the order of events, some of these events are reversible, for example, due to temperature cycling. However, certain characteristics exist for irreversible events, which help identify when they occurred. Below are listed these indicators along with general example definitions of appropriate indices. Where “…” is considered as input indicating comparable environmental conditions.

[0192] 1. Water Testing (SW)

[0193] I. The sensor closest to the surface reacts first, while the sensor closest to the substrate reacts last. This can be used to monitor progress over a period of time.

[0194] II. If the temperature is below the evaporation point of water:

[0195] III. Faster response than other events.

[0196] IV. Water on the surface is absorbed faster than water on the surface.

[0197] V. The modulus of the complex impedance decreases for all frequencies.

[0198]

[0199] For all frequencies ranging from 0.1 Hz to 100 kHz, the derivative is...

[0200]

[0201] VI. Larger capacitance and / or imaginary part of complex impedance

[0202]

[0203] and / or

[0204]

[0205] If the temperature is higher than the evaporation point of water, then the opposite can be observed.

[0206] 2. Degradation and Ion Transport (DI)

[0207] I. The sensor closest to the surface reacts first, and the sensor closest to the substrate reacts last. This can be used to monitor progress over a period of time.

[0208] II. Reduction of complex impedance modulus at all frequencies

[0209]

[0210] For all frequencies ranging from 0.1 Hz to 100 kHz, the derivative is...

[0211]

[0212] III. Resistance will increase.

[0213]

[0214] IV. Changes in the shape of complex impedance

[0215] 3. Water detection, degradation, and ion transport

[0216] I. Sometimes water detection, degradation, and ion transport are inseparable and can occur simultaneously.

[0217] 4. Corrosion (C)

[0218] I. Coatings available in the high-frequency domain capacitance (Generated by the imaginary part of the impedance) Exceed Coating under given conditions Saturation level This can be explained by the fact that when corrosion begins at the substrate-coating interface, it leads to a loss of adhesion, which results in the formation of new porous interfaces that can hold more water under humid conditions, i.e., in the form of bubbles. This phenomenon is usually accompanied by a decrease in impedance across the entire spectrum.

[0219]

[0220] II. At low frequencies, the impedance decreases to below the typical level at which the coating balances with the environment. That is, it is saturated with water under given temperature conditions. This is due to the decrease in coating resistance near the substrate-coating interface, which occurs due to coating degradation and the leaching of corrosion products into the coating, which are more conductive than the original coating.

[0221]

[0222] Where f is a low frequency less than 1Hz.

[0223] III. The third sign of corrosion is the appearance of a new time constant in the impedance spectrum. This is the result of creating a new interface on which charge transfer is frequency-dependent. In short, it can be viewed as the formation of a double-layer capacitor and a charge transfer resistor.

[0224] IV. Careful evaluation is often required to distinguish between degradation and corrosion, as they appear similar in the figures. However, the former occurs within the bulk, while the latter occurs at the interface between the coating and the substrate. This can be addressed by placing sensors at different coating depths to measure the bulk and coating-substrate interfaces separately.

[0225] An example of applying a general indicator formula.

[0226] Figure 16 The index for the change in the imaginary part of the complex impedance is shown, given as...

[0227]

[0228] Measurements were taken at different times t throughout the experiment for plates of 150 μm (circular), 300 μm (x), and 450 μm.

[0229] Here we describe how this indicator relates to different phenomena. See... Figure 17 :

[0230] 1. Water absorption

[0231] Arrow 1: Water absorption of the plate at 150µm and 300µm. The increase occurs within a short duration (approximately 200 hours) and saturates.

[0232] 2. Water absorption, degradation, and ion transport

[0233] Arrow 2: Water absorption, degradation, and ion transport at plate 450µm. This occurs over a short period, but longer than the time mentioned above (approximately 350 hours). Furthermore, the response is much larger, thus multiple phenomena occur simultaneously.

[0234] 3. Degradation and ion transport

[0235] Arrow 3: The plate at 300µm now increases further to 1500 hours. Furthermore, other parameters and shape changes become more similar to the 450µm plate.

[0236] 4. The transition from coating degradation to corrosion

[0237] Substrate corrosion is often a consequence of coating degradation, so these two processes can occur simultaneously. Both processes are characterized by a reduction in impedance below the value at which the coating balances with its environment in the early stages of its lifespan. However, substrate corrosion causes a more significant impedance reduction than degradation alone, and the change in the coating-substrate interface is accompanied by a new time constant in the impedance spectrum. These are general indicators for assessing coating condition through single-sensor measurements, but the accuracy of estimating the effects of corrosion and degradation can be greatly improved by evaluating the impedance response obtained from embedded sensors at different depths of the coating.

[0238] as follows Figure 19 Examples are shown in the diagram. The aim is to illustrate typical transitions in the EIS spectrum that can be correlated with various stages of coating aging, as achieved through accelerated testing in this case.

[0239] Figure 19 The diagram shows the first measurement of the impedance modulus (circle), and the measurement (x) after approximately 200 hours of initial saturation, similar to... Figure 17 Measurements were taken after the greywater was absorbed, and a final measurement was taken at approximately 1450 hours (*). Figure 19 In the graph, the horizontal axis represents the frequency in Hz, while the vertical axis represents the Zabs[ohm].

[0240] As the coating degrades significantly, the curves change characteristics and exhibit certain features. Observe the changes from the ~200-hour curve to the ~1450-hour curve:

[0241] I. Reduction of impedance at lower frequencies (arrow 191)

[0242] II. Reduction of impedance at high frequencies (arrow 192)

[0243] III. General Changes in the Overall Shape of the Spectrum

[0244] List of numbered embodiments

[0245] 1. A coated structure having a monitoring system (1), the coated structure comprising a substrate (2) having a substrate surface (3), a coating (4) coupled to the substrate surface in a substrate interface (5) and extending in the thickness direction (6) to an outer coating surface (7), a sensor (8, 9, 10, 11) including at least one electrode embedded in the coating, an I / O device (28) configured to generate an input signal in the sensor and read an output AC signal from the sensor, a data logger (28) configured to record the output signal from the I / O device, and a computer unit (12) configured to process the recorded signal from the data logger to determine at least two separate indicators, each indicator being related to the properties of the coating or the substrate.

[0246] 2. The structure according to Embodiment 1, wherein the sensor includes at least two electrodes.

[0247] 3. The structure according to Example 1 or 2, wherein the computer unit is configured to determine at least one of the at least two indicators by electrochemical impedance spectroscopy (EIS).

[0248] 4. The structure according to any of the foregoing embodiments, wherein the computer unit is configured to determine at least one of the two indicators by means of an input signal in the form of a pulse, wave, triangle, or alternating current.

[0249] 5. The structure according to any of the foregoing embodiments, wherein the sensor includes at least three electrodes, and wherein the computer unit is configured to determine one of the two indicators by using a first set of two of the three electrodes via EIS, and to determine the other of the two indicators by using a second set of two of the at least three electrodes via EIS.

[0250] 6. According to the structure described in Embodiment 5, the first set includes a first electrode and a second electrode, and the second set includes a second electrode and a third electrode.

[0251] 7. The structure according to any one of embodiments 1-5, wherein the sensor includes at least four electrodes, wherein the first set includes a first electrode and a second electrode, and the second set includes a third electrode and a fourth electrode.

[0252] 8. The structure according to any one of embodiments 5-7, wherein the input signal defines a first electric field between a first set of electrodes and a second electric field between a second set of electrodes, and wherein the first electric field and the second electric field define field curves with different sizes or shapes.

[0253] 9. According to the structure described in Example 8, the field curve of the first electric field is smaller than the field curve of the second electric field for a specific field strength.

[0254] 10. The structure according to embodiment 8 or 9, wherein the field curve of the first electric field with a specific field strength extends to the surface of the outer coating, and the field curve of the second electric field with the same specific field strength does not extend to the surface of the outer coating.

[0255] 11. The structure according to any one of embodiments 8-10, wherein the field curve of the first electric field with a specific field strength extends to the substrate interface, and the field curve of the second electric field with the same specific field strength does not extend to the substrate interface.

[0256] 12. The structure according to any one of embodiments 5-11, wherein the distance between the electrodes of the first set of electrodes is different from the distance between the electrodes of the second set of electrodes.

[0257] 13. The structure according to any one of embodiments 7-12, wherein the size of the electrodes of the first set of electrodes is different from the size of the electrodes of the second set of electrodes.

[0258] 14. The structure according to any one of embodiments 7-12, wherein the shape, construction and / or material of the electrodes of the first set of electrodes is different from the shape, construction and / or material of the electrodes of the second set of electrodes.

[0259] 15. The structure according to any of the foregoing embodiments, wherein the computer unit is configured to use the recorded signals to simultaneously define the at least two separate metrics.

[0260] 16. The structure according to any of the foregoing embodiments, wherein the coating comprises at least a first layer and a second layer, each layer comprising opposing inner and outer surfaces, the inner surfaces being coupled at a coating interface and the outer surface of the first layer being coupled to the substrate at a substrate interface.

[0261] 17. The structure according to embodiment 16, wherein at least one of the at least two electrodes of the sensor is located in the coating interface.

[0262] 18. The structure according to any one of embodiments 16-17, wherein the first layer has a first thickness and the second layer has a second thickness different from the first thickness.

[0263] 19. The structure according to any of the foregoing embodiments, wherein one of the at least two indicators is related to the substrate interface, and the other of the at least two indicators is related to the outer coating surface.

[0264] 20. The structure according to any of the foregoing embodiments, wherein the computer unit is configured to use the resistance in one of the at least two electrodes of the sensor to determine an index related to cracking in the coated structure.

[0265] 21. The structure according to any of the foregoing embodiments, wherein the computer unit is configured to receive configuration data recorded during the curing of the coating and generate a reference pattern based on the configuration data, and the computer unit is further configured to use the reference pattern to determine the degradation level of the coating.

[0266] 22. The structure according to embodiment 21 further includes a temperature sensor configured to determine the temperature of the coating, and wherein the computer unit is configured to receive temperature data from the temperature sensor.

[0267] 23. The structure according to embodiment 22, wherein the computer unit is configured to use temperature data in the process of determining the degradation level of the coating.

[0268] 24. The structure according to embodiments 21-22, wherein the computer unit is configured to use the reference pattern by comparing the reference pattern with the recorded output data.

[0269] 26. The structure according to any of the foregoing embodiments, wherein the computer unit is configured to provide one of the at least two indicators to relate it to a characteristic selected from the group consisting of: the presence of water, degradation of the coating, cracking of the substrate and / or coating, and corrosion of the substrate, and wherein the computer unit is configured to provide another of the at least two indicators to relate it to the same characteristic or another characteristic selected from the same group.

[0270] 27. The structure according to any of the foregoing embodiments, wherein the computer unit is configured to provide a combined value of the two separate indicators.

[0271] 28. The structure according to any of the foregoing embodiments, wherein the combined value is calculated based on a predefined function of the at least two separate indices.

[0272] 29. The structure according to any of the foregoing embodiments includes at least two electrodes located at the same level in the coating, and wherein two of the at least two indicators are related to signals recorded from the electrodes at the same level.

[0273] 30. The structure according to any of the foregoing embodiments includes at least two electrodes located at different levels in the coating, and wherein two of the at least two indicators are related to signals recorded from the electrodes at different levels.

[0274] 31. The structure according to any of the foregoing embodiments includes at least two electrodes located at different levels in the coating and laterally displaced relative to each other in a direction parallel to the substrate surface, wherein two of the at least two indicators are related to signals recorded from the electrodes at different levels.

[0275] 32. The structure according to any of the foregoing embodiments, wherein the I / O device is configured to generate an input signal in the form of a frequency scan, and wherein the computer unit (12) is configured to use the signal recorded from the data logger and determine at least two separate metrics based on the same frequency scan.

[0276] 33. The structure according to any of the foregoing embodiments includes at least one external electrode not embedded in the coating, the external electrode being attached to the surface of the outer coating.

[0277] 34. The structure according to any of the foregoing embodiments, wherein the I / O device is configured to generate input signals with different characteristics, including sinusoidal AC signals and pulsed DC signals, and wherein the computer unit is configured to process the recorded signal according to one of the characteristics of the input signal to determine a first index, and to process the recorded signal according to another of the characteristics to determine a second index.

[0278] 35. The structure according to any of the foregoing embodiments, wherein the computer unit is programmed with a first algorithm applied to the output signal to obtain a first index, and is programmed with a second algorithm applied to the output signal to obtain a second index.

[0279] 36. An insulating structure is formed according to any of the foregoing embodiments, wherein the coating is located between the substrate and the insulating material.

[0280] 37. The structure according to any of the foregoing embodiments, wherein the substrate forms a conduit.

[0281] 38. The structure according to any one of embodiments 1-35, wherein the substrate forms the interior of the tank, such as the interior of a storage tank or ballast tank.

[0282] 39. A monitoring system for integration into a coated structure, the coated structure comprising a structure having a substrate surface, a coating coupled to the substrate surface at a substrate interface and extending in the thickness direction to an outer coating surface, and including at least one electrode embedded in the coating.

[0283] The monitoring system includes:

[0284] -I / O devices are configured to generate input signals in sensors and read output signals from sensors.

[0285] - A data logger, configured to record output signals from I / O devices, and

[0286] - A computer unit is configured to process signals recorded from a data logger to determine at least two separate metrics, each of which is related to the properties of the coating or structure.

[0287] 40. The monitoring system according to embodiment 39, wherein the I / O device is configured to generate input signals in the form of frequency scanning, and wherein the computer unit (12) is configured to use signals recorded from the data logger and determine at least two separate indicators based on the same frequency scan.

[0288] 41. The monitoring system according to embodiment 39 or 40, wherein the computer unit is configured to provide a combined value of the two separate indicators.

[0289] 42. The monitoring system according to any one of embodiments 39-41, wherein the computer unit is configured to provide one of the at least two indicators to correlate with a characteristic selected from the group consisting of: the presence of water, degradation of the coating, cracking of the substrate and / or coating, and corrosion of the substrate, and wherein the computer unit is configured to provide another of the at least two indicators to correlate with the same characteristic or another characteristic selected from the same group.

[0290] 43. A method for monitoring the condition of a coated structure, the coated structure comprising a structure having a substrate surface, a coating coupled to the substrate surface at a substrate interface and extending in the thickness direction to an outer coating surface, and a sensor including at least one electrode embedded in the coating.

[0291] The method includes the following steps:

[0292] - Generate input signals in the sensor and read output signals from the sensor.

[0293] - Use a computer unit to determine at least two separate metrics based on the output signal, each metric being related to the properties of the coating or structure.

[0294] 44. The method according to Example 43, wherein at least one index is defined as a reference index obtained during the curing of the coating.

Claims

1. A coated structure with a monitoring system, the coated structure comprising: a substrate having a substrate surface, a coating coupled to the substrate surface in a substrate interface and extending in a thickness direction to an outer coating surface, a sensor comprising at least one electrode embedded in the coating, an I / O device configured to generate an input signal in the sensor and to read an output signal from the sensor, wherein the output signal is an AC signal, a data logger configured to record the output signal from the I / O device, and a computer unit configured to process the recorded signal from the data logger to determine at least two separate indices, each index relating to a property of the coating or the substrate, wherein the at least two separate indices express different properties and the at least two separate indices are combined to define a condition value expressing a further condition of the coated structure, the condition value depending on several separate indices, wherein the different properties are selected from water diffusion, degradation, ion presence, corrosion or cracking.

2. The coated structure according to claim 1, wherein the computer unit is configured to determine at least one of the at least two separate indices by electrochemical impedance spectroscopy (EIS).

3. The coated structure according to claim 1, wherein the computer unit is configured to determine at least one of the at least two separate indices by the input signal in the form of a pulse, or a wave or triangle, or an alternating current.

4. The coated structure according to claim 1, wherein the computer unit is configured to define the at least two separate indices simultaneously using the recorded signal.

5. The coated structure according to claim 1, wherein the coating comprises at least a first layer and a second layer, each layer comprising opposite inner and outer surfaces, the inner surface being coupled in a coating interface and the outer surface of the first layer being coupled to the substrate in a substrate interface.

6. The coated structure according to claim 5, wherein at least one of the electrodes of the sensor is located in the coating interface.

7. The coated structure according to claim 5, wherein the first layer has a first thickness and the second layer has a second thickness different from the first thickness.

8. The coated structure according to claim 1, wherein one of the at least two separate indices relates to the substrate interface and another one of the at least two separate indices relates to the outer coating surface.

9. The coated structure according to claim 1, wherein the computer unit is configured to receive configuration data recorded during curing of the coating, to generate a reference pattern based on the configuration data, and to determine a level of degradation of the coating based on the reference pattern.

10. The coated structure according to claim 1, wherein the computer unit is configured to provide one of the at least two separate indices to relate to a selected property, and wherein the computer unit is configured to provide another one of the at least two separate indices to relate to the same property or another property.

11. The coated structure according to claim 1, comprising at least two electrodes located at the same level in the coating, and wherein the computer unit is configured to determine the at least two separate indices simultaneously using the at least two electrodes. wherein two of the at least two separate indicators relate to signals recorded from electrodes at the same level.

12. The coated structure according to claim 1, comprising at least two electrodes at different levels in the coating, and wherein two of the at least two separate indicators relate to signals recorded from electrodes at different levels.

13. The coated structure according to claim 1, comprising at least two electrodes at different levels in the coating and laterally displaced relative to each other in a direction parallel to the surface of the substrate, and wherein two of the at least two separate indicators relate to signals recorded from electrodes at different levels.

14. The coated structure according to claim 1, wherein the I / O device is configured to generate the input signal in the form of a frequency sweep, and wherein the computer unit is configured to determine the at least two separate indicators using the recorded signals from the data logger and based on the same frequency sweep.

15. The coated structure according to claim 1, wherein the I / O device is configured to generate the input signal with different characteristics, including a sinusoidal AC signal and a pulsed DC signal, and wherein the computer unit is configured to process the recorded signals from the input signal of one of the characteristics to determine a first indicator and to process the recorded signals from the input signal of another of the characteristics to determine a second indicator.

16. The coated structure according to claim 1, wherein the computer unit is programmed with a first algorithm applied to the output signal to obtain a first indicator and with a second algorithm applied to the output signal to obtain a second indicator.

17. A monitoring system for integration in a coated structure, the coated structure comprising a structure having a substrate surface, a coating coupled to the substrate surface in a substrate interface and extending in a thickness direction to an outer coating surface, and at least one electrode embedded in the coating, the monitoring system comprising: an I / O device configured to generate an input signal in the sensor and to read an output signal from the sensor, a data logger configured to record the output signal from the I / O device, and a computer unit configured to process the recorded signals from the data logger to determine at least two separate indicators, each indicator relating to a property of the coating or structure, wherein the at least two separate indicators express different properties, and the at least two separate indicators are combined to define a condition value expressing a further condition of the coated structure, the condition value depending on several separate indicators, wherein the different properties are selected from water diffusion, degradation, ion presence, corrosion or cracking.

18. The monitoring system according to claim 17, wherein the I / O device is configured to generate the input signal in the form of a frequency sweep, and wherein the computer unit is configured to determine the at least two separate indicators using the recorded signals from the data logger and based on the same frequency sweep.

19. The monitoring system according to claim 17, wherein the computer unit is configured to provide one of the at least two separate indicators to relate it to a selected property, and wherein the computer unit is configured to provide another of the at least two separate indicators to correlate it with the same property or another property.

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