Measurement method for corrosion amount and selection method for metal material

Abstract

An electrical resistance–type corrosion sensor 1 is to be installed on a metal part 16 of a mobile body 15. The corrosion sensor 1 comprises a sensor part 2 that is exposed to an arbitrary environment and a reference part 3 that is shielded from the arbitrary environment, and conductors that constitute the sensor part 2 and the reference part 3 comprise the same metal material that constitutes the metal part 16. The corrosion amount of the sensor part 2 is measured on the basis of the electrical resistance value of the sensor part 2 and the electrical resistance value of the reference part 3. The present invention thereby makes it possible to accurately ascertain the corrosion amount of the metal part 16 of the mobile body 15.

Description

Methods for measuring corrosion levels and selecting metal materials

[0001] The present invention relates to a method for measuring the amount of corrosion and a method for selecting a metal material.

[0002] Mobile objects such as automobiles, ships, aircraft, and heavy machinery have at least a portion made of metal. The concept of a mobile object also includes movable objects such as cranes and conveyor belts (the same applies hereinafter).

[0003] Metal parts of mobile objects are subject to damage and deterioration over time. One of the causes of damage and deterioration is corrosion. In order to use mobile objects safely and for a long period of time, it is important to understand the amount of corrosion (corrosion rate) of metal parts of the mobile object under actual operating conditions.

[0004] As a moving object moves, the way sunlight hits the metal parts of the moving object changes. This causes changes in the wet / dry state and the state of adhesion and detachment of corrosive substances such as airborne salt on the metal parts of the moving object. Therefore, the amount of corrosion on the metal parts of a moving object varies greatly depending on the movement of the moving object and the position of the metal parts on the moving object.

[0005] For example, Patent Document 1 discloses a technique for determining the degree of corrosion in metal parts of a moving body, which describes a method for measuring a corrosive environment of a moving body, comprising: (a) providing, at one or more parts of the moving body, at least a portion of which is made of a metallic material, two types of metal electrodes having different components and / or compositions, one of which is a metallic material from which a constituent component of the moving body material is to be selected, and the other of which is made of the same metal but a different metal that is nobler in the electrochemical hierarchy than the first metal; and (b) providing one or more corrosion sensors arranged such that a gap between at least one pair of electrodes is 0.1 to 5 mm across an insulator; and continuously or intermittently measuring the current or potential difference between the electrodes caused by an electrical short circuit between the electrodes in a corrosive environment, including during movement; and (c) including installing the corrosion sensors inside the moving body and isolated from the outside, or inside a constituent part of the moving body ([Claim 1]).

[0006] In Patent Document 1, an ACM type corrosion sensor (Non-Patent Documents 1 and 2) is used.

[0007] JP 2009-53205 A

[0008] Zairyo-to-Kankyo, Japan Society of Corrosion Engineering, 2005, Vol. 54, No. 8, pp. 375-382 Zairyo-to-Kankyo, Japan Society of Corrosion Engineering, 2002, Vol. 51, No. 9, pp. 398-403

[0009] In an atmospheric corrosion monitor (ACM) type corrosion sensor, the galvanic current flowing between two dissimilar metals exposed to a corrosive environment while insulated from each other is measured, and the amount of corrosion is calculated based on an empirical formula. However, because corrosion progresses as a result of a combination of various factors, the amount of corrosion calculated by an ACM type corrosion sensor may not necessarily match the actual amount of corrosion.

[0010] The present invention has been made in view of the above points, and an object of the present invention is to provide a method for measuring the amount of corrosion that can accurately grasp the amount of corrosion of a metal part of a moving body.

[0011] As a result of extensive research, the present inventors have found that the above object can be achieved by employing the following configuration, and have completed the present invention.

[0012] That is, the present invention provides the following [1] to

[10] . [1] A method for measuring the amount of corrosion, comprising: attaching a corrosion sensor to a metal part of a mobile body having a metal part made of a metal material; the corrosion sensor being an electrical resistance corrosion sensor having a sensor part made of a conductor exposed to an arbitrary environment and a reference part made of a conductor isolated from the arbitrary environment, the conductor being made of the same metal material as the metal material constituting the metal part; and measuring the amount of corrosion of the sensor part based on the electrical resistance values ​​of the reference part and the sensor part. [2] The method for measuring the amount of corrosion according to [1] above, wherein the corrosion sensor has an insulating sheet, and the reference part is in contact with the metal part only via the insulating sheet. [3] A method for measuring the amount of corrosion, comprising attaching a corrosion sensor to the metal part of a mobile body having a metal part made of a metal material, the corrosion sensor being an electrical resistance type corrosion sensor having a sensor part made of a conductor exposed to an arbitrary environment and a reference part made of a conductor isolated from the arbitrary environment, the conductor being made of the same metal material as the metal material constituting the metal part. ２[K] or more. [4] The method for measuring the amount of corrosion according to any one of [1] to [3] above, wherein the sensor unit and the reference unit are laminated with an insulator interposed between them. [5] The method for measuring the amount of corrosion according to any one of [1] to [3] above, wherein the measured amount of corrosion of the sensor unit is acquired at a location remote from the mobile object by communication using a communication device. [6] The method for measuring the amount of corrosion according to [4] above, wherein the measured amount of corrosion of the sensor unit is acquired at a location remote from the mobile object by communication using a communication device. [7] A method for selecting a metal material for the metal part based on the amount of corrosion of the sensor unit measured by the method for measuring the amount of corrosion according to any one of [1] to [3] above. [8] A method for selecting a metal material for the metal part based on the amount of corrosion of the sensor unit measured by the method for measuring the amount of corrosion according to [4] above. [9] A method for selecting a metal material for the metal part based on the amount of corrosion of the sensor unit measured by the method for measuring the amount of corrosion according to [5] above.

[10] A method for selecting a metal material for constituting the metal part, based on the amount of corrosion of the sensor part measured by the method for measuring the amount of corrosion described in [6] above.

[0013] According to the present invention, the amount of corrosion of the metal parts of a moving body can be determined with high accuracy.

[0014] Fig. 3 is a plan view schematically showing a corrosion sensor of a first embodiment. Fig. 4 is a cross-sectional view taken along line A-A in Fig. 1. Fig. 5 is a plan view schematically showing a corrosion sensor of a second embodiment. Fig. 6 is a cross-sectional view taken along line B-B in Fig. 3. Fig. 7 is a cross-sectional view of the corrosion sensor for explaining the connection state with a current source and a voltage measurement unit. Fig. 8 is a view showing a state in which the corrosion sensor 1 is attached to a metal part of a moving body.

[0015] [Method for Measuring the Amount of Corrosion] The following describes a method for measuring the amount of corrosion of the present invention. The following description also serves as a description of a method for selecting a metal material of the present invention. In the method for measuring the amount of corrosion of the present invention, an electrical resistance corrosion sensor is first attached to a metal portion of a mobile object. The corrosion sensor includes a sensor portion exposed to an arbitrary environment and a reference portion isolated from the arbitrary environment, and the conductors constituting the sensor portion and the reference portion are made of the same metal material as the metal portion of the mobile object. The amount of corrosion of the sensor portion is then measured based on the electrical resistance values ​​of the reference portion and the sensor portion. In the present invention, the conductors of the corrosion sensor are made of the same metal material as the metal portion of the mobile object, and the amount of corrosion is calculated directly from the electrical resistance value without using an empirical formula. This allows the amount of corrosion of the metal portion of the mobile object to be accurately determined.

[0016] <Corrosion Sensor> First, the basic configuration of an electrical resistance corrosion sensor used in the present invention will be described with reference to Figures 1 and 2 (first embodiment) and Figures 3 to 5 (second embodiment). However, the corrosion sensor that can be used in the present invention is not limited to the following embodiments.

[0017] First Embodiment Fig. 1 is a plan view schematically showing a corrosion sensor 1 according to a first embodiment. Fig. 2 is a cross-sectional view taken along line A-A in Fig. 1. The electrical resistance corrosion sensor 1 has a sensor section 2 that is exposed to an arbitrary environment, and a reference section 3 that is isolated from the arbitrary environment to which the sensor section 2 is exposed. The sensor section 2 and the reference section 3 are both made of a conductor and are arranged in parallel on one surface of a flat insulating sheet 4.

[0018] The "any environment" to which the sensor unit 2 is exposed is a concept that encompasses various environments, including a "corrosive environment" that corrodes the sensor unit 2. In other words, the corrosion sensor 1 may be used not only in a corrosive environment that corrodes the sensor unit 2, but also in an environment that does not corrode the sensor unit 2.

[0019] 2, the cross sections of the sensor part 2 and the reference part 3 are rectangular (including square) with a predetermined thickness. Both side surfaces of the sensor part 2 and the reference part 3 are covered with insulating resin 5, and the top surface of the reference part 3 is covered with an insulating cover 6.

[0020] 2, when the corrosion sensor 1 is viewed in cross section, both side surfaces and the top and bottom surfaces of the rectangular reference portion 3 are covered with various members. Therefore, even when the corrosion sensor 1 is in a corrosive environment, the reference portion 3 is isolated from the corrosive environment.

[0021] On the other hand, the upper surface of the sensor unit 2 is not covered by the cover 6. That is, when the corrosion sensor 1 is viewed in cross section as shown in FIG. 2 , both side surfaces and the lower surface of the rectangular sensor unit 2 are covered with respective members, but the upper surface is exposed. Therefore, when the corrosion sensor 1 is in a corrosive environment, the upper surface of the sensor unit 2 is exposed to this corrosive environment. When the upper surface of the sensor unit 2 is exposed to the corrosive environment, corrosion progresses in its thickness direction (from the upper surface to the lower surface).

[0022] Next, each part of the corrosion sensor 1 will be described in more detail.

[0023] (Insulating Sheet) As will be described later, it is preferable to make the temperature of the reference part 3 of the corrosion sensor 1 equal to the temperature of the metal part 16 (see FIG. 6 ) of the moving body 15. For this reason, when attaching the corrosion sensor 1 to the metal part 16, it is preferable to bring the reference part 3 (and the sensor part 2) into contact with the metal part 16 only via the insulating sheet 4.

[0024] The material of the insulating sheet 4 is not particularly limited as long as it is a material that does not electrically connect the reference part 3 and the sensor part 2 to the metal part 16 of the moving body 15, and examples thereof include glass, ceramics, plastic (synthetic resin), and natural resin.

[0025] The insulating sheet 4 preferably has good thermal conductivity, i.e., high thermal conductivity (high thermal conductivity). Specifically, the thermal conductivity of the insulating sheet 4 is preferably 0.3 W / (m·K) or more, more preferably 0.5 W / (m·K) or more, and even more preferably 1.0 W / (m·K) or more. The thermal conductivity of the insulating sheet 4 may be 3.0 W / (m·K) or more. On the other hand, there is no particular upper limit, and the thermal conductivity of the insulating sheet 4 may be, for example, 100.0 W / (m·K) or less, 50.0 W / (m·K) or less, 30.0 W / (m·K) or less, or 10.0 W / (m·K) or less.

[0026] A suitable material for such an insulating sheet 4 is, for example, polyimide.

[0027] The thickness of the insulating sheet 4 (the length in the vertical direction in FIG. 2 ) may be any thickness that can insulate the reference part 3 and the sensor part 2 from the metal part 16, and is, for example, 5 μm or more, preferably 10 μm or more. On the other hand, from the viewpoint of obtaining good thermal conductivity, the thickness of the insulating sheet 4 is preferably 50 μm or less, more preferably 40 μm or less, and even more preferably 30 μm or less.

[0028] The thermal conductivity of the insulating sheet 4 is set to 25 kW / (m ２ ·K) or more is preferable, and 40 kW / (m ２ ·K) or more is more preferable, and 70 kW / (m ２ ·K) or more is more preferable, and 100 kW / (m ２ A heat transmission coefficient of kW / (m·K) or more is most preferable. There is no particular upper limit, and the higher the heat transmission coefficient, the better. The heat transmission coefficient of the insulating sheet 4 is obtained by dividing the thermal conductivity of the insulating sheet 4 (unit: kW / (m·K)) by the thickness of the insulating sheet 4 (unit: m).

[0029] (Resin) The material of the resin 5 is not particularly limited, and any conventionally known material can be used, such as epoxy resin, phenol resin, polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), nylon, etc. The thickness of the resin 5 corresponds to the thickness of the sensor portion 2 and the reference portion 3.

[0030] (Cover) The material of the cover 6 is not particularly limited, and conventionally known materials can be used, such as rubber and paint, with weather-resistant materials being preferred. The thickness of the cover 6 is not particularly limited, and may be, for example, 0.1 to 10 mm.

[0031] (Sensor unit and reference unit) The conductors constituting the sensor unit 2 and the reference unit 3 are made of the same metal material as the metal material constituting the metal unit 16 of the moving body 15 (see FIG. 6). Examples of such metal materials include iron and iron alloys. The iron content in the iron alloy is preferably 90 mass % or more. Examples of elements other than iron contained in the iron alloy include at least one element selected from the group consisting of carbon, silicon, manganese, phosphorus, and sulfur; and elements that improve corrosion resistance, such as copper and nickel.

[0032] The shape of the conductors constituting the sensor unit 2 and the reference unit 3 is preferably a long piece having a certain length, for example, a meandering shape with bends at certain intervals as shown in Fig. 1. The sensor unit 2 and the reference unit 3 may be, for example, a continuous, long piece of conductor as shown in Fig. 1.

[0033] The length (total length) of the sensor unit 2 is preferably 30 mm or more, more preferably 100 mm or more, while the length (total length) of the sensor unit 2 is preferably 500 mm or less, more preferably 400 mm or less.

[0034] When the sensor unit 2 is viewed in cross section as shown in Figure 2, the width of the sensor unit 2 (the horizontal distance in Figure 2) is preferably 4 mm or more, and more preferably 5 mm or more, from the viewpoint of averaging out and mitigating the effect of a sudden increase in electrical resistance even when deep localized corrosion occurs on the upper surface (surface) of the sensor unit 2. On the other hand, if the width of the sensor unit 2 is too wide, the electrical resistance may become too small, making it difficult to perform highly accurate measurements, and therefore the width is preferably 15 mm or less, more preferably 12 mm or less, and even more preferably 10 mm or less.

[0035] The thickness of the sensor portion 2 (the vertical distance in FIG. 2 ) is preferably 50 μm or more, and more preferably 100 μm or more, from the viewpoint of ease of processing the conductor when processing the conductor to obtain the sensor portion 2. On the other hand, the thickness of the sensor portion 2 is preferably 1000 μm or less, and more preferably 600 μm or less, from the viewpoint of improving the measurement accuracy of the corrosion sensor 1.

[0036] The shape of the reference part 3 is preferably the same as that of the sensor part 2. This eliminates the need to correct the difference in electrical resistance value caused by the difference in shape from the sensor part 2.

[0037] These numerical ranges for the sensor part 2 and the reference part 3 are determined from the viewpoint of, for example, the measurement accuracy of the corrosion sensor 1, the ease of handling the corrosion sensor 1, the amount and form of corrosion, and the like.

[0038] (Current Source and Voltage Measurement Unit) As described above, the sensor unit 2 and the reference unit 3 may be a continuous series of conductors. In this case, a current source 7 is connected to both ends of the series of conductors that make up the sensor unit 2 and the reference unit 3, a voltage measurement unit 8 is connected to both ends of the sensor unit 2, and a voltage measurement unit 9 is connected to both ends of the reference unit 3.

[0039] A constant current is applied from the current source 7, and the voltage is measured by the voltage measuring units 8 and 9, thereby determining the electrical resistance values ​​of the sensor unit 2 and the reference unit 3. Then, as will be described later, the amount of corrosion of the sensor unit 2 is calculated based on the determined electrical resistance values.

[0040] (Logger) The corrosion sensor 1 preferably further includes a logger 11 (see FIG. 6 ). The logger 11, for example, drives the current source 7 at any interval to pass a constant current, causes the voltage measurement unit 8 and the voltage measurement unit 9 to measure voltage, determines the electrical resistance values ​​of the sensor unit 2 and the reference unit 3, and calculates the amount of corrosion of the sensor unit 2 based on the determined electrical resistance values. The logger 11 can then record data such as the calculated amount of corrosion.

[0041] (Communication Device) The corrosion sensor 1 preferably further includes a communication device 12 (see FIG. 6 ). The various data recorded in the logger 11 are uploaded to a cloud or the like by communication using the communication device 12.

[0042] Second Embodiment Next, a corrosion sensor 21 according to a second embodiment will be described with reference to Figures 3 to 5. The same reference numerals are used for the same parts as those in the first embodiment described with reference to Figures 1 and 2, and descriptions thereof will be omitted.

[0043] Fig. 3 is a plan view schematically showing a corrosion sensor 21 according to the second embodiment. Fig. 4 is a cross-sectional view taken along line BB in Fig. 3, showing an enlarged view of the vicinity of the sensor portion 2 and the reference portion 3.

[0044] 4, the reference part 3 made of a conductor is disposed on an insulating sheet 4. The sensor part 2 made of a conductor is disposed on one surface of the reference part 3 opposite to the insulating sheet 4, with an insulator 10 interposed therebetween. That is, the sensor part 2 and the reference part 3 are stacked with the insulator 10 interposed therebetween.

[0045] The material of the insulator 10 is not particularly limited as long as it does not electrically connect the sensor unit 2 and the reference unit 3, and examples thereof include glass, ceramics, plastic (synthetic resin), and natural resin. Since poor thermal conductivity of the insulator 10 can easily cause a temperature difference between the sensor unit 2 and the reference unit 3, it is preferable to select a material with as high a thermal conductivity as possible. If the insulator 10 is too thick, its thermal conductivity is likely to be poor, while if it is too thin, there is a high risk of electrical short-circuiting. The preferred thickness of the insulator 10 varies depending on the material, but is preferably 5 to 200 μm, for example, when the insulator 10 is a plastic film such as polyvinyl chloride, polyethylene, or polypropylene.

[0046] It is preferable to tightly contact the insulator 10 with the sensor part 2 and the reference part 3 so that no gaps are formed between them. This is because gaps can easily impair thermal conductivity. For this reason, it is preferable to press the insulator 10 with the sensor part 2 and the reference part 3 with sufficient force or to bond them together using a thermally conductive adhesive. When bonding, it is preferable to thoroughly clean the bonding surfaces to remove any dirt or dust.

[0047] 5 is a cross-sectional view of the corrosion sensor 21 for illustrating the connection state between the current source 7 and the voltage measurement unit 8. As shown in Fig. 5, the voltage measurement unit 8 is connected to terminal 2a, which is one end of the sensor unit 2, and terminal 2b, which is the other end, and the voltage measurement unit 9 is connected to terminal 3a, which is one end of the reference unit 3, and terminal 3b, which is the other end. Terminal 2b of the sensor unit 2 and terminal 3b of the reference unit 3 are electrically connected, and the current source 7 is connected to terminal 2a of the sensor unit 2 and terminal 3a of the reference unit 3.

[0048] In the following description, unless otherwise specified, for convenience, the “corrosion sensor 21” will also be referred to as the “corrosion sensor 1.” Such a corrosion sensor 1 is attached to the metal part 16 of the moving body 15.

[0049] <Mobile body (attaching corrosion sensor to mobile body)> Fig. 6 is a diagram showing a state in which the corrosion sensor 1 is attached to a metal part 16 of a mobile body 15. Fig. 6 shows a case in which the mobile body 15 is an automobile. However, the mobile body 15 is not limited to an automobile, and other examples include ships, aircraft, heavy machinery, etc. Furthermore, the mobile body 15 also includes movable bodies such as cranes and belt conveyors.

[0050] At least a part of the mobile object 15 is a metal part 16 made of a metal material. When the mobile object 15 is an automobile, the metal part 16 is, for example, the body of the automobile.

[0051] Here, consider the case where a heat source other than the atmosphere (e.g., direct sunlight) causes a temperature change in the metal part 16 of the moving object 15. The temperature change in the metal part 16 is affected by the heat capacity of the metal part 16. Therefore, the temperature change of the corrosion sensor 1, which is smaller than the moving object 15 (metal part 16), differs from that of the metal part 16. Temperature affects the speed of the corrosion reaction and the wetness and dryness of the water film required for the corrosion reaction.

[0052] Therefore, in order to improve the measurement accuracy of the corrosion sensor 1, it is preferable to make the temperature of the corrosion sensor 1 match the temperature of the moving body 15. Specifically, it is preferable to make the temperature of the reference part 3 of the corrosion sensor 1 match the temperature of the metal part 16 of the moving body 15. Therefore, when attaching the corrosion sensor 1 to the metal part 16, it is preferable to bring the reference part 3 into contact with the metal part 16 only via the insulating sheet 4.

[0053] In practice, the insulating sheet 4 and the metal part 16 are bonded together using an adhesive, or the insulating sheet 4 and the metal part 16 are brought into close contact with each other using grease and then the periphery is hardened with a sealant. In this way, the corrosion sensor 1 is fixed to the metal part 16. That is, in practice, an adhesive, grease, or the like may be interposed between the reference part 3 and the metal part 16 in addition to the insulating sheet 4. However, even in this case, in the present invention, the reference part 3 of the corrosion sensor 1 is considered to be in contact with the metal part 16 of the moving body 15 only via the insulating sheet 4.

[0054] The thermal conductivity of the adhesive and grease is preferably 1.0 W / (m·K) or more. When bonding the various parts of the corrosion sensor 1 together (for example, when bonding the reference part 3 and the insulating sheet 4), it is preferable to use the same adhesive.

[0055] The number of corrosion sensors 1 attached to one moving body 15 is at least one, and may be two or more. For example, even for the same moving body 15, the amount of corrosion may vary depending on the position of the metal part 16. In such cases, multiple corrosion sensors 1 are attached to one moving body 15. Furthermore, multiple corrosion sensors 1 may be attached to one moving body 15 to improve measurement accuracy.

[0056] Depending on the shape of the moving body 15, the area in which the corrosion sensor 1 can be installed may be narrow. In this case, the corrosion sensor 21 of the second embodiment (FIGS. 3 to 5), in which the sensor unit 2 and the reference unit 3 are stacked, is preferable to the corrosion sensor 1 of the first embodiment (FIGS. 1 and 2), in which the sensor unit 2 and the reference unit 3 are arranged in parallel, because the area in contact with the metal part 16 is smaller.

[0057] <Measurement of Corrosion Amount> In the corrosion sensor 1 attached to the mobile object 15, a constant current is applied from the current source 7, and the voltage is measured by the voltage measurement units 8 and 9, thereby determining the electrical resistance values ​​of the sensor unit 2 and the reference unit 3. The magnitude of the constant current can be set arbitrarily based on, for example, the required measurement accuracy and amount of power.

[0058] As the corrosion of the sensor part 2 progresses, the electrical resistance of the sensor part 2 gradually increases from its initial value. On the other hand, the corrosion of the reference part 3 does not progress, and the electrical resistance of the reference part 3 basically remains unchanged from its initial value.

[0059] The reason why the progression of corrosion of the sensor unit 2 is related to an increase in electrical resistance is generally thought to be as follows: As corrosion progresses, the conductor that makes up the sensor unit 2 thins in the thickness direction. The thinned conductor is either lost from the surface or is replaced by corrosion products and remains on the surface. These corrosion products are non-conductors, or, if they are conductors, have much lower conductivity than the original conductors. As a result, the increase in electrical resistance due to corrosion is considered to be due to thinning of the conductor that makes up the sensor unit 2.

[0060] The electrical resistance values ​​of the sensor part 2 and the reference part 3 are determined at any regular interval, and the corrosion amount (corrosion depth) of the sensor part 2 is calculated (converted) based on the determined electrical resistance values. The corrosion amount conversion formula is expressed by the following formula (1): CD = t ｉ {(R ｒｉ / R ｓｉ )-(R ｒ / R ｓ )} ... (1) CD: amount of corrosion (corrosion depth) [μm] t ｉ : initial thickness of the sensor part [μm] R ｒｉ : Initial electrical resistance value of the reference part [Ω] Rｓｉ : Initial electrical resistance value of the sensor part [Ω] R ｒ : Electrical resistance value of the reference part at the time of measurement [Ω] R ｓ : Electrical resistance value of the sensor part during measurement [Ω]

[0061] The corrosion amount is calculated based on the above formula (1) under an assumption. For example, if the initial thicknesses of the reference part 3 and the sensor part 2 are both "100 μm" and the initial electrical resistance value of the reference part 3 (R ｒｉ ) and the initial electrical resistance value (R ｓｉ ) are both "0.1Ω", and the electrical resistance value (R ｒ ) has remained unchanged at "0.1Ω" since the beginning, but on the other hand, as corrosion of the sensor part 2 progresses, the electrical resistance value (R ｓ ) has increased to "0.11 Ω", the amount of corrosion is calculated from the above formula (1) as 100×{(0.1 / 0.1)−(0.1 / 0.11)}, which is "9.1 μm".

[0062] <Temperature Compensation, etc.> It is preferable to further perform temperature compensation in the corrosion sensor 1. That is, when the electrical resistance value of the reference part 3 changes, it is preferable to correct the measured corrosion amount based on this change, assuming that this change is caused by a temperature change.

[0063] In general, the higher the temperature of a metal, the higher its electrical resistivity. For example, in the above assumption, if the temperature is higher than the initial temperature and the electrical resistance (R ｓ ) is not "0.11Ω" but is 10% more, or "0.121Ω." In this case, if we calculate 100 × {(0.1 / 0.1) - (0.1 / 0.121)} using the above formula (1), the amount of corrosion becomes "17 μm," which is significantly different from the original amount of corrosion of "9.1 μm."

[0064] However, at this time, for example, the electrical resistance value (R ｒSimilarly, if the resistance of the wire changes from 0.1 Ω to 0.11 Ω, a 10% increase, due to a temperature rise, the amount of corrosion can be corrected based on this change. That is, the amount of corrosion is calculated from the above formula (1) as 100 × {(0.1 / 0.1) - (0.11 / 0.121)}, which is 9.1 μm, and the same result as when there is no temperature change is obtained.

[0065] As mentioned above, by matching the temperature of the reference part 3 with the temperature of the metal part 16, the effectiveness of the temperature compensation is increased.

[0066] The entity that performs the above-described corrosion amount measurement and temperature compensation is not particularly limited, but may be, for example, the logger 11. The logger 11, for example, calculates the corrosion amount of the sensor unit 2 while performing temperature compensation, and records data such as the calculated corrosion amount. The corrosion amount and other data recorded in the logger 11 are uploaded to the cloud or the like via communication using the communication device 12. By downloading the uploaded data, a user of the corrosion sensor 1 can grasp the corrosion amount of the sensor unit 2 and the like at any time, even if the user is in any location away from the mobile object 15.

[0067] The user of the corrosion sensor 1 can use the determined amount of corrosion for various purposes. For example, the user can perform maintenance on the mobile object 15 so that the amount of corrosion does not exceed the corrosion allowance of the metal part 16 (the amount of corrosion that is tolerable for the metal part 16) during the expected period of use of the mobile object 15. In addition, the user can select a metal material for the metal part 16 based on the determined amount of corrosion so that the amount of corrosion does not exceed the corrosion allowance of the metal part 16 during the expected period of use of the mobile object 15.

[0068] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the examples described below.

[0069] The test was carried out under the conditions shown in the following Table 1. Specifically, a corrosion sensor was attached to a moving body and a test was carried out to measure the amount of corrosion, as will be described below.

[0070] <Moving objects> First, four types of moving objects (including movable objects) with metal parts were selected: automobiles, heavy machinery, cranes, and belt conveyors. The types of moving objects selected are shown in Table 1 below. The metal parts of the automobiles, heavy machinery, and cranes are their respective bodies. The metal part of the belt conveyor is the belt (conveyor belt).

[0071] <Corrosion Sensor> Corrosion sensors were attached to the metal parts of the selected moving bodies. One corrosion sensor was attached to each moving body.

[0072] <<Nos. 1 to 20: Electrical Resistance-Type Corrosion Sensor>> In Nos. 1 to 20, the electrical resistance-type corrosion sensor 21 (FIGS. 3 to 5) of the second embodiment was used as the corrosion sensor.

[0073] (Nos. 1 to 5 and 7 to 20) More specifically, referring to Figs. 3 to 5, an insulating sheet 4 made of polyimide (thickness: 25 µm, thermal conductivity: 1.0 W / (m·K), thermal transmittance: 40 kW / (m ２ The reference unit 3 was placed on the insulating sheet 4. Resin 5, which is epoxy resin, was spread evenly on the insulating sheet 4 to the same thickness as the reference unit 3, covering both side surfaces of the reference unit 3. An insulator 10, which is a plastic film (polyvinyl chloride, thickness: 100 μm), was placed on top of that, and the sensor unit 2 was placed so as to overlap the reference unit 3 with the insulator 10 in between. Resin 5, which is epoxy resin, was spread evenly on the insulator 10 to the same thickness as the sensor unit 2, covering both side surfaces of the sensor unit 2. The conductors (metal material) constituting the sensor unit 2 and the reference unit 3 were long conductors (total length: 200 mm, width: 10 mm, thickness: 200 μm), and were made of the same metal material as the metal parts of the target moving object (such as the body of an automobile). The insulating sheet 4 of such a corrosion sensor 21 was adhered to the metal part of the target moving body (such as the body of a car) using a highly thermally conductive adhesive (thermal conductivity: 2.1 W / (m·K)).

[0074] (No. 6) Insulating sheet 4 (thickness: 25 μm, heat transmission coefficient: 12 kW / (m ２Corrosion sensors 21 (Figs. 3 to 5) were fabricated in the same manner as Nos. 1 to 5 and 7 to 20, except that the corrosion sensor 21 used was the insulating sheet thermal conductivity. In the "Insulating Sheet Thermal Conductivity" column in Table 1 below, No. 6 is marked "low," and the other examples are marked "-."

[0075] <Nos. 21 to 30> The corrosion sensors used were either an ACM-type corrosion sensor, an electrochemical impedance spectroscopy (EIS) corrosion sensor, or a quartz crystal microbalance (QCM)-type corrosion sensor. For the measurement of the corrosion amount using an ACM-type corrosion sensor, Non-Patent Documents 1 and 2 were referenced.

[0076] <Direct sunlight> Some metal parts of a moving object are exposed to direct sunlight, a heat source other than the atmosphere, and some are not. In the "Heat source" column of Table 1 below, "Yes" is entered if the corrosion sensor is installed in a location exposed to direct sunlight, and "-" is entered if the corrosion sensor is installed in a location not exposed to direct sunlight.

[0077] <Temperature synchronization> When an electrical resistance corrosion sensor was used and the reference part of the corrosion sensor was attached in contact with the metal part of the moving body via only an insulating sheet, "Yes" was entered in the "Temperature synchronization" column in Table 1 below. On the other hand, when a spacer (stainless steel plate "SUS304", thickness: 2 mm) was placed between the insulating sheet and the metal part of the moving body, "-" was entered in the "Temperature synchronization" column in Table 1 below. Note that "-" was also entered when a corrosion sensor that is not an electrical resistance type was used.

[0078] <Environment> The corrosion environment for the mobile bodies was the atmosphere in all cases. However, the area in which the mobile bodies were used varied for each example. If the mobile body was used in area A, where the amount of airborne salt was low, it was marked "low airborne salt." If it was used in area B, where the amount of airborne salt was higher than area A, it was marked "high airborne salt." If it was used in a snowy, cold region where snow-melting salt is sprayed, it was marked "snow-melting salt." Furthermore, if the mobile body was used in a situation where it came into contact with soil, it was marked "+ soil." If it was used in a situation where it came into contact with coal, it was marked "+ coal."

[0079] <Duration> The test period was approximately 3 months (between 89 and 105 days).

[0080] <Amount of corrosion (sensor)> After the test period had elapsed, the amount of corrosion (unit: μm) was measured using a corrosion sensor attached to the metal part of the mobile body. When an electrical resistance type corrosion sensor was used, the amount of corrosion at the sensor part was measured. The measured amount of corrosion is shown in the "Sensor" column of "Amount of corrosion" in Table 1 below.

[0081] <Amount of corrosion (test piece)> To compare with the amount of corrosion measured by the corrosion sensor, a test piece (described below) was attached adjacent to the corrosion sensor to the metal part of the moving body and allowed to corrode during the test period. After the test period had elapsed, the amount of corrosion of the test piece was determined. While the amount of corrosion of the metal part of the moving body should normally be measured, it is difficult to determine this non-destructively, so the amount of corrosion was determined using the test piece instead.

[0082] A 150mm x 70mm x 0.8mm cold-rolled steel plate (SPC material) was attached to the automobile as a test specimen. A 150mm x 70mm x 0.8mm rolled steel material for welded structures (SM material) was attached to the heavy machinery, crane, and belt conveyor as a test specimen.

[0083] The amount of corrosion of the test specimen was determined in accordance with ISO 8407. Specifically, after the test period had elapsed, rust was removed from the test specimen using a pickling solution prepared by adding 3.5 g of hexamethylenetetramine to 500 mL of hydrochloric acid to make a total volume of 1000 mL, and the amount of corrosion (unit: μm) was calculated from the difference in mass before and after the test. The calculated amount of corrosion is shown in the "Test specimen" column of "Amount of corrosion" in Table 1 below.

[0084] <Error> The error (unit: %) between the amount of corrosion determined using the corrosion sensor and the amount of corrosion of the test piece was determined. The smaller the absolute value of the error, the better the accuracy of the amount of corrosion determined using the corrosion sensor can be evaluated. In particular, when the absolute value of the error is 10% or less, the accuracy can be evaluated as being better.

[0085]

[0086] <Summary of Evaluation Results> As shown in Table 1 above, Nos. 1 to 20 (invention examples), which used electrical resistance corrosion sensors, had smaller absolute values ​​of error than Nos. 21 to 30 (comparison examples), which used other corrosion sensors, and it can be said that the amount of corrosion of the metal parts of the moving body was grasped with high accuracy.

[0087] Of Nos. 1 to 20, Nos. 11 and 12 (examples where "Direct sunlight" was "Yes" but "Temperature synchronization" was "-") had an absolute error value of over 10%. In contrast, Nos. 1 to 10 and 13 to 20 had absolute error values ​​of 10% or less, demonstrating better accuracy.

[0088] Furthermore, when comparing No. 5 and No. 6, which differ only in the thermal conductivity of the insulating sheet among No. 1 to No. 20, No. 5, which has a higher thermal conductivity of the insulating sheet, had a smaller absolute value of error and better accuracy than No. 6, which has a lower thermal conductivity of the insulating sheet.

[0089] The corrosion amounts of Nos. 21 to 25, which used ACM-type corrosion sensors, generally tended to be greater than the amount of corrosion of the test specimens. In particular, the corrosion amounts of Nos. 23 and 24, which were tested in contact with coal, deviated significantly from the amount of corrosion of the test specimens. This is thought to be because coal dust that had accumulated on the ACM-type corrosion sensors retained moisture caused by rainfall, etc., resulting in high output throughout the test period.

[0090] Nos. 26 to 28, which used an EIS corrosion sensor, also had large absolute values ​​of errors and insufficient accuracy, similar to Nos. 21 to 25, which used an ACM-type corrosion sensor.

[0091] In samples No. 29 to 30, which used a QCM-type corrosion sensor, the amount of corrosion could not be measured. This is thought to be because, in principle, a QCM-type corrosion sensor uses a thin film for measurement, and under the test conditions, the amount of corrosion exceeded the thickness of this thin film.

[0092] <Retest: No. 5b> A test to measure the amount of corrosion was conducted in the same manner as No. 5, except that 10 corrosion sensors were attached to one moving object (heavy machinery) (for convenience, referred to as "No. 5b"). As with No. 5, 10 corrosion sensors were attached to locations on the moving object that were exposed to direct sunlight. As a result, the error between the amount of corrosion determined using the corrosion sensors and the amount of corrosion on the test piece was 1.8%, which was even more accurate than No. 5.

[0093] 1: Corrosion sensor (first embodiment) 2: Sensor unit 2a: Terminal of sensor unit 2b: Terminal of sensor unit 3: Reference unit 3a: Terminal of reference unit 3b: Terminal of reference unit 4: Insulating sheet 5: Resin 6: Cover 7: Current source 8: Voltage measuring unit 9: Voltage measuring unit 10: Insulator 11: Logger 12: Communication device 15: Mobile object 16: Metal part 21: Corrosion sensor (second embodiment)

Claims

1. A method for measuring the amount of corrosion, comprising: attaching a corrosion sensor to a metal part of a mobile object having the metal part made of a metal material; the corrosion sensor being an electrical resistance type corrosion sensor having a sensor part made of a conductor exposed to an arbitrary environment and a reference part made of a conductor isolated from the arbitrary environment; the conductor being made of the same metal material as the metal material making up the metal part; and measuring the amount of corrosion of the sensor part based on the electrical resistance value of the reference part and the electrical resistance value of the sensor part.

2. The method for measuring the amount of corrosion according to claim 1, wherein the corrosion sensor has an insulating sheet, and the reference part contacts the metal part only via the insulating sheet.

3. The thermal conductivity of the insulating sheet is 25kW / (m ２ The method for measuring the amount of corrosion according to claim 2, wherein the corrosion rate is 100 kJ / s or more.

4. A method for measuring the amount of corrosion according to any one of claims 1 to 3, wherein the sensor section and the reference section are laminated with an insulator interposed therebetween.

5. A method for measuring the amount of corrosion described in any one of claims 1 to 3, in which the measured amount of corrosion of the sensor unit is obtained at a location away from the mobile body by communication using a communication device.

6. A method for measuring the amount of corrosion according to claim 4, wherein the measured amount of corrosion of the sensor unit is acquired at a location away from the mobile body by communication using a communication device.

7. A method for selecting a metal material for constituting the metal part, based on the amount of corrosion of the sensor part measured by the method for measuring the amount of corrosion described in any one of claims 1 to 3.

8. A method for selecting a metal material, which selects a metal material for forming the metal part based on the amount of corrosion of the sensor part measured by the method for measuring the amount of corrosion described in claim 4.

9. A method for selecting a metal material, which selects a metal material for forming the metal part based on the amount of corrosion of the sensor part measured by the method for measuring the amount of corrosion described in claim 5.

10. A method for selecting a metal material, which selects a metal material for forming the metal part based on the amount of corrosion of the sensor part measured by the method for measuring the amount of corrosion described in claim 6.

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