Apparatus and method for measuring corrosion amount and penetrated hydrogen amount of metallic material

Abstract

To provide an apparatus for measuring a corrosion amount and a penetrated hydrogen amount of a metallic material that can reduce a temperature difference of a test piece between corrosion amount measurement and hydrogen penetration amount measurement, and improve the accuracy in capturing the correlation between a corrosion rate and a hydrogen penetration rate.SOLUTION: An apparatus for measuring a corrosion amount and a penetrated hydrogen amount of a metallic material according to the present invention comprises a test piece 1 having one surface 1a exposed to a corrosive environment, a test tank 2 in which the other surface 1b of the test piece 1 forms part of an inner wall and which is filled with an electrolyte solution 2a, a counter electrode 3 and a reference electrode 4 arranged inside the test tank 2, a potential and current control device 5 for measuring an anode current flowing between the test piece 1 and the counter electrode 3, a resistance measuring instrument 6 for measuring the electrical resistance of the test piece 1, and a temperature measuring instrument 7 for measuring the temperature of the electrolyte solution 2a and / or the test piece 1. The apparatus is configured to determine the corrosion amount of the test piece 1 on the basis of outputs from the resistance measuring instrument 6 and the temperature measuring instrument 7, and to determine the penetrated hydrogen amount into the test piece 1 on the basis of an output from the potential and current control device 5.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an apparatus and method for measuring the amount of corrosion and amount of absorbed hydrogen of a metallic material. [Background technology]

[0002] In recent years, metallic materials used in automobiles and various industrial machinery have been made stronger in order to reduce their weight. However, the higher the strength of metallic materials such as steel, the greater the likelihood of delayed fracture. Delayed fracture is a phenomenon in which a metallic material undergoes static load stress and suddenly breaks brittlely after a certain period of time, with little apparent plastic deformation. Delayed fracture is mainly caused by the penetration of some of the hydrogen generated when the metallic material is corroded in an atmospheric environment.

[0003] Because hydrogen penetration is closely related to the progression of atmospheric corrosion, a method for quantitatively evaluating both the rate at which hydrogen penetrates into a material and the rate at which corrosion progresses in an atmospheric environment is necessary to select materials with excellent delayed fracture resistance.

[0004] In Patent Document 1 listed below, a corrosion sensor is provided that determines the amount of corrosion from changes in electrical resistance as a method for measuring the amount or rate of corrosion of steel materials in an atmospheric environment, making it possible to monitor the progression of corrosion in an atmospheric environment.

[0005] Non-Patent Document 1 listed below provides a hydrogen permeation cell as a method for detecting the amount of hydrogen that penetrates into metals in atmospheric corrosion environments, in which the hydrogen penetration side of the device devised by Devanathan et al. is exposed to the atmosphere to detect the hydrogen that penetrates due to atmospheric corrosion. Patent Document 2 listed below also provides a method for measuring the amount of hydrogen penetration that is an improved version of the device in Non-Patent Document 1, in which multiple hydrogen permeation cells are placed in contact with a single test piece, and one of the cells is used as a reference cell that is not subject to corrosion, thereby correcting the residual current that changes with temperature. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-20735 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-179893 [Non-patent literature]

[0007] [Non-Patent Document 1] Ikeda, Y. et al., "Hydrogen absorption by carbon steel in atmospheric corrosion environments," Proceedings of the Symposium on Corrosion and Protection, vol. 42, pp. 565-568 (1994). Summary of the Invention [Problem to be solved by the invention]

[0008] As shown in the above-mentioned Patent Documents 1 and 2 and Non-Patent Document 1, individual measurements of the corrosion amount and the amount of absorbed hydrogen of metallic materials have been investigated. However, in order to analyze the hydrogen absorption behavior in an atmospheric corrosion environment, it is necessary to measure both the corrosion amount and the amount of absorbed hydrogen under the same environment.

[0009] As shown in Fig. 7, it is conceivable to simultaneously measure both the amount of corrosion and the amount of hydrogen penetration by arranging a conventional hydrogen permeation cell such as that provided in Patent Document 2 and Non-Patent Document 1 side by side with a conventional corrosion sensor such as that proposed in Patent Document 1. However, we have newly discovered that such a configuration would cause the following problems.

[0010] The inventors used 0.2 mm thick steel pieces as the corrosion test specimens and hydrogen permeation test specimens shown in Figure 7 and heated and cooled them. When the temperatures of the corrosion test specimens, hydrogen permeation test specimens, and electrolyte solution were measured, it was found that the hydrogen permeation test specimens placed in contact with the electrolyte solution and the corrosion test specimens not in contact with the electrolyte solution showed a large difference in their temperature response to environmental temperature changes, resulting in a difference in their temperature histories. This is thought to be due to the electrolyte solution having a larger heat capacity than the test specimens.

[0011] In order to accurately grasp the correlation between the corrosion rate and the hydrogen entry rate in an atmospheric environment where temperature changes repeatedly, it is necessary to determine both rates for test specimens where the temperature changes equally. However, when the hydrogen permeation cell and the corrosion sensor are placed side by side as described above, a temperature difference occurs between the test specimens, which reduces the accuracy of grasping the correlation between the corrosion rate and the hydrogen entry rate.

[0012] The present invention has been made to solve the above-mentioned problems, and one of its objects is to provide an apparatus and method for measuring the corrosion rate and the amount of absorbed hydrogen of a metallic material, which can reduce the temperature difference of the test piece between the corrosion rate measurement and the amount of absorbed hydrogen measurement, and can improve the accuracy of determining the correlation between the corrosion rate and the hydrogen absorption rate. [Means for solving the problem]

[0013] In one embodiment, the device for measuring the amount of corrosion and the amount of hydrogen that has penetrated into a metal material according to the present invention comprises: a test piece made of a plate-shaped metal material, one side of which is exposed to a corrosive environment and is subject to corrosion; a test tank, the other side of which forms part of the inner wall and which is filled with an electrolyte solution; a counter electrode and a reference electrode disposed inside the test tank for detecting the flux of hydrogen that penetrates into the test piece from one side and diffuses to the other side as an anode current; a potential / current control device that measures the anode current flowing between the test piece and the counter electrode; a resistance meter that measures the electrical resistance of the test piece; and a temperature meter that measures the temperature of the electrolyte solution and / or the test piece, and is configured to determine the amount of corrosion of the test piece based on the outputs of the resistance meter and the temperature meter, and to determine the amount of hydrogen that has penetrated into the test piece based on the output of the potential / current control device.

[0014] In one embodiment, the method for measuring the amount of corrosion and the amount of absorbed hydrogen of a metallic material according to the present invention includes determining the amount of corrosion of a test piece from the electrical resistance of the test piece, which is placed so that one surface is exposed to a corrosive environment and the other surface forms part of the inner wall of a test tank filled with an electrolyte solution, and from the temperature of the electrolyte solution and / or the test piece, and determining the amount of absorbed hydrogen into the interior of the test piece from the anodic current due to the flux of hydrogen that penetrates into the test piece from one surface and diffuses to the other surface. [Effects of the Invention]

[0015] According to one embodiment of the device and method for measuring the amount of corrosion and the amount of hydrogen penetration of a metallic material of the present invention, both the amount of corrosion and the amount of hydrogen penetration are determined from a test specimen that is placed so that one surface is exposed to a corrosive environment and the other surface forms part of the inner wall of a test tank filled with an electrolyte solution.Therefore, compared to when a hydrogen permeation cell and a corrosion sensor are placed side by side, the temperature difference of the test specimen between the corrosion amount measurement and the hydrogen penetration amount measurement can be made smaller, and the correlation between the corrosion rate and the hydrogen penetration rate can be more accurately determined. [Brief explanation of the drawings]

[0016] [Figure 1]1 is an explanatory diagram showing the configuration of an apparatus for measuring the amount of corrosion and the amount of absorbed hydrogen of a metal material according to an embodiment of the present invention; [Figure 2] FIG. 2 is a front view showing the test piece of FIG. 1. [Figure 3] FIG. 3 is a front view showing a first modified example of the test piece 1 of FIG. 2. [Figure 4] FIG. 3 is a front view showing a second modified example of the test piece 1 of FIG. [Figure 5] 2. FIG. 4 is a front view showing a third modified example of the test piece 1 of FIG. [Figure 6] 2 is a graph showing the temperature history of a test piece, an electrolyte solution, and a corrosion test piece when the device for measuring the amount of corrosion and the amount of absorbed hydrogen of a metal material shown in FIG. 1 and a conventional corrosion sensor are arranged side by side. [Figure 7] FIG. 1 is an explanatory diagram showing a state in which a conventional hydrogen permeation cell and a conventional corrosion sensor are arranged side by side. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to each embodiment, and the components can be modified and embodied without departing from the spirit of the present invention. Furthermore, various inventions can be formed by appropriately combining multiple components disclosed in each embodiment. For example, some components may be omitted from all the components shown in the embodiments. Furthermore, components of different embodiments may be appropriately combined.

[0018] Fig. 1 is an explanatory diagram showing the configuration of an apparatus for measuring the amount of corrosion and the amount of absorbed hydrogen of a metallic material according to an embodiment of the present invention, Fig. 2 is a front view of the test piece 1 of Fig. 1, Fig. 3 is a front view of a first modified example of the test piece 1 of Fig. 2, Fig. 4 is a front view of a second modified example of the test piece 1 of Fig. 2, and Fig. 5 is a front view of a third modified example of the test piece 1 of Fig. 2. Some components such as the test tank body 20 are not shown in Figs. 2 to 5.

[0019] The measuring device of this embodiment is an apparatus for measuring the amount of corrosion and the amount of hydrogen penetration of a metal material. As shown in Figures 1 and 2, the measuring device includes a test piece 1, a test tank 2, a counter electrode 3, a reference electrode 4, a potential / current control device 5, a resistance measuring device 6, and a temperature measuring device 7.

[0020] The test piece 1 is a test object for measuring the amount of corrosion and the amount of absorbed hydrogen. The test piece 1 is made of a plate-shaped metal material and is positioned so that one surface 1a is exposed to a corrosive environment and is corroded.

[0021] Any material may be used as the metallic material constituting the test piece 1. The metallic material may be, for example, zinc, copper, or aluminum, but is typically steel. One surface 1a exposed to a corrosive environment may be referred to as the surface or the corrosion / hydrogen penetration surface. One surface 1a may be exposed without being coated. Alternatively, one surface 1a may be coated with a surface treatment layer such as zinc plating or painting. Examples of corrosive environments include an environment heated by a heat source such as sunlight, an environment where drying and wetting occur repeatedly (e.g., an environment where humidity fluctuates depending on the temperature difference between day and night), and an environment where various liquid droplets adhere (e.g., an environment exposed to rainfall, sprayed salt water, melted snow salt water, seawater, splashes (splash-like or mist-like) of salt water, and corrosive liquids).

[0022] The test tank 2 has the other surface 1b of the test piece 1 as a part of its inner wall, and is filled with an electrolyte solution 2a.

[0023] Any container capable of containing the electrolyte solution 2a and the like can be used as the test tank 2, but since it is expected to be exposed to a corrosive environment for a long period of time, a container made of glass, resin, or the like, which has excellent insulating and weather-resistant properties, is usually used. In particular, from the viewpoint of ease of processing and handling, a container made of resin is preferable, and a container made of polyvinyl chloride resin or acrylic resin is more preferable.

[0024] Any electrolyte solution 2a may be used as long as its solution resistance is sufficiently low so that the oxidation of hydrogen atoms diffusing from one surface 1a of the test piece 1 to the other surface 1b to hydrogen ions is the rate-limiting step in measuring the amount of absorbed hydrogen. The solution resistance can be reduced by increasing the electrolyte concentration in the electrolyte solution 2a. When the solution resistance is high, the rate-limiting step is not the oxidation of hydrogen atoms to hydrogen ions, but rather the rate at which the current flowing through the electrochemical measurement system through the electrolyte solution 2a. If the pH of the electrolyte solution 2a is less than 9, it may be difficult to maintain the passivity of the other surface 1b of the test piece 1 during anodic current measurement. Therefore, the pH of the electrolyte solution 2a is preferably 9 or higher. On the other hand, if the pH is too high, i.e., too alkaline, the electrolyte solution may cause significant damage to the environment if it leaks outside due to an accident or other reason. Therefore, the pH of the electrolyte solution 2a is preferably 13 or lower. An example of the electrolyte solution 2a that satisfies these conditions and can be suitably used is an aqueous NaOH solution of about 0.1 to 1.0 M (M = mol / L). From the viewpoints of preventing leakage of the electrolyte solution 2a and ease of handling, it is also preferable to use a gel electrolyte instead of a liquid electrolyte.

[0025] The other surface 1b, which is part of the inner wall of the test chamber 2, may be referred to as the back surface or the hydrogen detection surface. The other surface 1b may be subjected to a surface treatment so that the metal base of the test piece 1 does not come into direct contact with the electrolyte solution 2a. Examples of the surface treatment include Pd or Ni plating.

[0026] The counter electrode 3 and the reference electrode 4 are placed inside the test chamber 2 and are used to detect the flux of hydrogen that penetrates the test piece 1 from one surface 1a and diffuses to the other surface 1b as an anode current.

[0027] A cathode current of the same amount as the anode current flowing through the test piece 1 flows through the counter electrode 3. Any inert electrode can be used as the counter electrode 3, as long as its surface area is large enough so that the cathode reaction caused by the flowing cathode current does not become the rate-limiting step in measuring the amount of absorbed hydrogen. The surface area of ​​the counter electrode 3 is preferably equal to or larger than the surface area of ​​the region of the test piece 1 that comes into contact with the electrolyte solution 2a. Examples of suitable counter electrodes 3 include a platinum (Pt) electrode and a glassy carbon electrode.

[0028] The reference electrode 4 is an electrode that serves as a reference potential when measuring the anode current in the measurement device of this embodiment. There are no particular limitations on the reference electrode 4, and various electrodes currently in practical use, such as those used in general electrochemical measurements, can be used. However, when using an electrode containing chloride, such as a silver-silver chloride electrode (SSE), care must be taken because leaked chloride ions may contaminate the electrolyte solution 2a, destroying the passivity of the sample surface and resulting in inaccurate measurement of the anode current. An example of a reference electrode that does not contaminate the electrolyte solution with chloride is an Ir / Ir oxide electrode.

[0029] The potential / current control device 5 is a device that measures the anodic current that flows between the test piece 1 and the counter electrode 3. The potential / current control device 5 is sometimes called a potentiostat. The potential / current control device 5 is electrically connected to the test piece 1, the counter electrode 3, and the reference electrode 4.

[0030] The resistance meter 6 is a device that measures the electrical resistance of the test piece 1. The resistance meter 6 may measure the voltage when a predetermined current is applied to the test piece 1, and obtain the electrical resistance of the test piece 1 from the values ​​of the current and voltage.

[0031] The temperature measuring device 7 is a device that measures the temperature of the electrolyte solution 2a and / or the test piece 1. In the measurement device of this embodiment, the other surface 1b of the test piece 1 is part of the inner wall of the test tank 2. In other words, the test piece 1 is arranged so as to be in contact with the electrolyte solution 2a. As will be described later, when the test piece 1 is heated or cooled, the temperature history of the test piece 1 substantially coincides with the temperature history of the electrolyte solution 2a.

[0032] The temperature measuring device 7 is, for example, a thermocouple. In the illustrated embodiment, the temperature measuring device 7 is disposed inside the test tank 2 at a position away from the test specimen 1 so as to measure the temperature of the electrolyte solution 2a. However, the temperature measuring device 7 is not limited to this and may be any device that can measure the temperature of the electrolyte solution 2a and / or the test specimen 1. For example, the temperature measuring device 7 may be an electrical resistance temperature sensor or a non-contact temperature sensor such as an infrared radiation thermometer. A non-contact temperature measuring device 7 may be disposed outside the test tank 2 to measure the temperature of the test specimen 1.

[0033] The measuring device of this embodiment is configured to determine the amount of corrosion of the test piece 1 based on the outputs of the resistance measuring device 6 and the temperature measuring device 7, and to determine the amount of hydrogen that has penetrated into the test piece 1 based on the output of the potential / current control device 5. In other words, the measuring device of this embodiment is configured to determine the amount of corrosion and the amount of hydrogen that has penetrated from the same test piece 1.

[0034] The electrical resistance of the test piece 1 is R (Ω), and the length and cross-sectional area of ​​the test piece 1 related to the measurement of the electrical resistance are L (m) and S (m 2 ), the electrical resistance is expressed as "R = ρ(L / S)" as is well known. Here, "ρ" is the resistivity (Ωm) of test piece 1, and when the temperature of test piece 1 is t (℃) and the resistivity at a given temperature is "ρ0", the resistivity is expressed as "ρ0(1 + αt)". α is a temperature coefficient known for each material. When corrosion occurs in test piece 1, the cross-sectional area of ​​test piece 1 decreases, and the electrical resistance of test piece 1 increases accordingly. By observing the electrical resistance and temperature, the decrease in the cross-sectional area of ​​test piece 1, i.e., the amount of corrosion of test piece 1, can be determined.

[0035] Some of the hydrogen generated by corrosion on one surface 1a of the test specimen 1 penetrates the specimen as interstitial hydrogen atoms and diffuses to the other surface 1b, driven by the concentration gradient within the specimen 1. By maintaining the surface potential of the other surface 1b at a potential sufficient for the ionization of hydrogen, the hydrogen atoms that reach the other surface 1b by diffusion release electrons and become hydrogen ions. The potential / current control device 5 maintains the electrode potential of the other surface 1b at a potential sufficient for the ionization of hydrogen atoms, and the anodic current associated with the release of electrons is measured. The hydrogen permeation current can be obtained by subtracting the passivation current measured under conditions without interstitial hydrogen from this anodic current. Therefore, the amount of hydrogen that penetrates into the specimen 1 can be determined based on the output of the potential / current control device 5.

[0036] As explained using Figure 7, when a hydrogen permeation cell, which determines the amount of hydrogen that has penetrated into the interior of test piece 1, and a corrosion sensor, which determines the amount of corrosion of test piece 1, are arranged side by side, a temperature difference occurs between the test piece of the hydrogen permeation cell (hydrogen permeation test piece) and the test piece of the corrosion sensor (corrosion test piece), which reduces the accuracy of determining the correlation between the corrosion rate and the hydrogen penetration rate.

[0037] In contrast, the measurement device of this embodiment determines both the amount of corrosion and the amount of absorbed hydrogen from a test specimen 1 that is placed so that one surface 1a is exposed to a corrosive environment and the other surface 1b forms part of the inner wall of a test tank 2 filled with an electrolyte solution 2a. Therefore, compared to the case where a hydrogen permeation cell and a corrosion sensor are placed side by side as shown in Figure 7, the temperature difference between the test specimen 1 when measuring the amount of corrosion and the amount of absorbed hydrogen can be made smaller, and the correlation between the corrosion rate and the hydrogen absorbed rate can be more accurately determined.

[0038] 1 and 2, the resistance measuring instrument 6 has a pair of resistance measurement terminals 6a connected to the test piece 1, and the test piece 1 has a corrosion monitoring area 10 located between the pair of resistance measurement terminals 6a. It is preferable that a large portion of the other surface 1b of the corrosion monitoring area 10 is in contact with the electrolyte solution 2a. By having a large portion of the other surface 1b of the corrosion monitoring area 10 in contact with the electrolyte solution 2a, the temperature difference between the area of ​​the test piece 1 where the corrosion amount is determined (corrosion monitoring area 10) and the area of ​​the test piece 1 where the amount of absorbed hydrogen is determined can be more reliably reduced, and the correlation between the corrosion rate and the hydrogen absorption rate can be more accurately determined.

[0039] As shown in FIG. 2, the test piece 1 may be rectangular. When the test piece 1 has a longitudinal direction 1L and a transverse direction 1S, the pair of resistance measurement terminals 6a may be arranged spaced apart from each other in the longitudinal direction 1L. The pair of resistance measurement terminals 6a may be arranged at positions (inner) away from both ends of the test piece 1 in the longitudinal direction 1L. The corrosion monitoring area 10 may be understood as an area in which the pair of resistance measurement terminals 6a are located at both ends in the longitudinal direction 1L of the test piece 1 and which has the same width as the test piece 1 in the transverse direction 1S of the test piece 1. The corrosion monitoring area 10 may also be understood as an area on the test piece 1 between straight lines extending in the transverse direction 1S of the test piece 1 at the respective positions of the pair of resistance measurement terminals 6a.

[0040] The test chamber 2 may include a test chamber body 20 (see FIG. 1) having a front surface 20b with an opening 20a. The test specimen 1 may be disposed adjacent to the front surface 20b of the test chamber body 20 so as to close the opening 20a. The opening 20a may have an outer shape similar to a smaller version of the test specimen 1. When the test specimen 1 is rectangular as shown in FIG. 2, the opening 20a may also be rectangular.

[0041] In FIG. 2, the combined area of ​​the white-painted area and the hatched area on the test piece 1 is the corrosion monitoring area 10, and the other surface 1b of the corrosion monitoring area 10, which is the hatched area, is in contact with the electrolyte solution 2a through the opening 20a. When the test piece 1 is viewed from the front as shown in FIG. 2, if the area of ​​the opening 20a is more than 50% of the area of ​​the corrosion monitoring area 10, it can be understood that most of the other surface 1b of the corrosion monitoring area 10 is in contact with the electrolyte solution 2a. The area of ​​the opening 20a is preferably 65% ​​or more of the area of ​​the corrosion monitoring area 10, more preferably 80% or more, and even more preferably 90% or more. If the area of ​​the opening 20a is 80% or more (or 90% or more) of the area of ​​the corrosion monitoring area 10, it can be understood that the other surface 1b of the corrosion monitoring area 10 is in contact with the electrolyte solution 2a entirely. When the other surface 1b of the corrosion monitoring area 10 is in full contact with the electrolyte solution 2a, the temperature difference between the area where the amount of corrosion of the test piece 1 is determined (corrosion monitoring area 10) and the area where the amount of absorbed hydrogen of the test piece 1 is determined can be reduced even more reliably.

[0042] If the test piece 1 is a rectangle (square) that does not have a longitudinal direction 1L or a lateral direction 1S, the pair of resistance measurement terminals 6a may be arranged spaced apart in the direction in which the first side of the test piece 1 extends, and the corrosion monitoring area 10 may be understood to be the area on the test piece 1 between the straight lines extending parallel to the second side perpendicular to the first side of the test piece 1 at each position of the pair of resistance measurement terminals 6a.

[0043] The outer shape of the test piece 1 is not limited to a rectangle, but may be other shapes such as a circle (see FIG. 3), a U-shape (see FIG. 4), or an M-shape (see FIG. 5).

[0044] 3, when the test piece 1 is circular, the pair of resistance measurement terminals 6a may be arranged spaced apart in the radial direction of the test piece 1, and may be arranged so that the center point of the test piece 1 is located between them. When the test piece 1 is circular, the corrosion monitoring area 10 may be understood as the area on the test piece 1 between the lines extending in a direction perpendicular to the direction in which the pair of resistance measurement terminals 6a are spaced apart at each position of the pair of resistance measurement terminals 6a.

[0045] Although not shown, when the test piece 1 is elliptical, the pair of resistance measurement terminals 6a may be arranged spaced apart in the long axis direction of the test piece 1, and may be arranged so that the center point of the test piece 1 is located between them. When the test piece 1 is elliptical, the corrosion monitoring area 10 may be understood as the area on the test piece 1 between straight lines extending in a direction (short axis direction) perpendicular to the direction in which the pair of resistance measurement terminals 6a are spaced apart (long axis direction) at each position of the pair of resistance measurement terminals 6a.

[0046] 4 and 5, when the test piece 1 is U-shaped or M-shaped, each part of the test piece 1 can be understood to be composed of a band portion extending in a U-shape or M-shape, and a pair of resistance measurement terminals 6a can be arranged at one end and the other end of the band portion in the direction of extension of the band portion. When the test piece 1 is U-shaped or M-shaped, the corrosion monitoring area 10 can be understood to be the area on the test piece 1 between the straight lines extending in a direction perpendicular to the direction in which the band portion extends at each position of the pair of resistance measurement terminals 6a.

[0047] 3 to 5, the combined area of ​​the white-painted area and the hatched area on the test piece 1 is the corrosion monitoring area 10, and the other surface 1b of the corrosion monitoring area 10 that is in contact with the electrolyte solution 2a through the opening 20a is shown. In the embodiments of FIGS. 3 to 5, when the area of ​​the opening 20a is more than 50% of the area of ​​the corrosion monitoring area 10 when viewed from the front of the test piece 1, it can be understood that most of the other surface 1b of the corrosion monitoring area 10 is in contact with the electrolyte solution 2a. In the embodiments of FIGS. 3 to 5, the area of ​​the opening 20a is preferably 65% ​​or more, more preferably 80% or more, and even more preferably 90% or more of the area of ​​the corrosion monitoring area 10. When the area of ​​the opening 20a is 80% or more (or 90% or more) of the area of ​​the corrosion monitoring area 10, it can be understood that the other surface 1b of the corrosion monitoring area 10 is in contact with the electrolyte solution 2a entirely. When the other surface 1b of the corrosion monitoring area 10 is in full contact with the electrolyte solution 2a, the temperature difference between the area where the amount of corrosion of the test piece 1 is determined (corrosion monitoring area 10) and the area where the amount of absorbed hydrogen of the test piece 1 is determined can be reduced even more reliably.

[0048] As described above, the measuring device of this embodiment measures the amount of corrosion of the test piece 1 based on the increase in electrical resistance that accompanies a decrease in the cross-sectional area of ​​the test piece 1. The smaller the initial thickness of the test piece 1, the greater the change in electrical resistance due to a decrease in thickness, and therefore the higher the measurement accuracy can be. On the other hand, if the initial thickness of the test piece 1 is reduced, the measurement period becomes shorter. The initial thickness of the test piece 1 varies depending on the type of metal, the environment, and the purpose of the measurement, so it cannot be generalized, but it is, for example, 0.1 to 10 mm, and preferably 0.2 to 1.0 mm. It is preferable that the initial thickness of the test piece 1 is uniform throughout the entire test piece 1.

[0049] For the same reasons as above, the narrower the width (the dimension perpendicular to the direction of current flow and the thickness direction) of the test piece 1 is, or the longer the length (the dimension along the direction of current flow) is, the higher the measurement accuracy can be. That is, the more elongated the test piece 1 is, such as the rectangular shape shown in FIG. 2 or the U- and M-shapes shown in FIGS. 4 and 5, the higher the measurement accuracy can be. On the other hand, if the test piece 1 is elongated, it becomes more susceptible to the effects of localized corrosion. Whether the test piece 1 is elongated or not can be changed depending on the goal of improving measurement accuracy or minimizing the effects of localized corrosion.

[0050] As described above, the test tank 2 may include a test tank body 20 (see FIG. 1 ) having a front surface 20b with an opening 20a, and the test piece 1 may be disposed adjacent to the front surface 20b of the test tank body 20 so as to cover the opening 20a. In this case, a pair of resistance measurement terminals 6a may be sandwiched between the front surface 20b of the test tank body 20 and the other surface 1b of the test piece 1. By adopting such a configuration, the positional relationship between the opening 20a and the resistance measurement terminals 6a can be easily determined compared to when the resistance measurement terminals 6a are disposed on one surface 1a of the test piece 1, and it is possible to more reliably ensure that a large portion of the other surface 1b of the corrosion monitoring area 10 comes into contact with the electrolyte solution 2a.

[0051] A portion of the wiring 6b connecting the pair of resistance measurement terminals 6a and the resistance meter 6 may also be sandwiched between the front surface 20b of the test tank body 20 and the other surface 1b of the test piece 1. A recess in which the pair of resistance measurement terminals 6a and the wiring 6b are embedded may be formed in the front surface 20b of the test tank body 20.

[0052] The potential / current control device 5 may have a test piece connection terminal 5a. As shown in FIG. 2, the test piece connection terminal 5a may be located outside the corrosion monitoring area 10 in the longitudinal direction 1L of the test piece 1. This configuration allows the test piece connection terminal 5a to be separated from the electrolyte solution 2a, reducing the risk of problems occurring when placing the test piece 1 on the front surface 20b of the test tank body 20. Like the pair of resistance measurement terminals 6a described above, the test piece connection terminal 5a may be sandwiched between the front surface 20b of the test tank body 20 and the other surface 1b of the test piece 1. A portion of the wiring 5b connecting the test piece connection terminal 5a to the potential / current control device 5 may also be sandwiched between the front surface 20b of the test tank body 20 and the other surface 1b of the test piece 1. A recess into which the test piece connection terminal 5a and the wiring 5b are embedded may be formed in the front surface 20b of the test tank body 20.

[0053] It is preferable that the measurement of the electrical resistance by the resistance meter 6 and the measurement of the anode current by the potential / current control device 5 are performed at different times. This is because if the measurement of the anode current by the potential / current control device 5 is performed while a current for measuring the electrical resistance is flowing through the test piece 1, the measurement accuracy of the anode current resulting from the amount of absorbed hydrogen may decrease. By performing the measurement of the electrical resistance by the resistance meter 6 and the measurement of the anode current by the potential / current control device 5 at different times, the influence of the measurement of the electrical resistance on the measurement of the anode current can be reduced. The measurement of the electrical resistance may be performed at intervals of, for example, about 1 to 30 minutes, and the measurement of the anode current may be performed at approximately the same interval as the measurement of the electrical resistance. It is preferable that the interval between the measurement of the electrical resistance and the measurement of the anode current is 5 seconds or more. The measurements by the potential / current control device 5 and the resistance meter 6 may be controlled by a control device (not shown).

[0054] The measuring device may further include a recording device 8 that records, in chronological order, the electrical resistance and temperature measured by the temperature measuring device 7 and the resistance measuring device 6, and the anodic current measured by the potential / current control device 5. The correlation between the corrosion rate and the hydrogen penetration rate may be investigated based on the electrical resistance, temperature, and anodic current recorded by the recording device 8. The recording method of the recording device 8 may be either digital or analog.

[0055] A method for measuring the amount of corrosion and the amount of absorbed hydrogen of a metal material according to an embodiment of the present invention includes the steps of: The test piece 1 is arranged so that one surface 1a is exposed to a corrosive environment and the other surface 1b forms part of the inner wall of a test tank 2 filled with an electrolyte solution 2a, and the amount of corrosion of the test piece 1 is determined from the electrical resistance of the test piece 1 and the temperature of the electrolyte solution 2a and / or the test piece 1; and The amount of hydrogen that penetrates into the test piece 1 is determined from the anodic current due to the flux of hydrogen that penetrates into the test piece 1 from one surface 1a and diffuses to the other surface 1b. That is, the measurement method of this embodiment determines the amount of corrosion and the amount of absorbed hydrogen from the same test piece 1.

[0056] The test piece 1 has a corrosion monitoring area 10 located between a pair of resistance measurement terminals 6a for measuring electrical resistance, and most of the other surface 1b of the corrosion monitoring area 10 may be in contact with the electrolyte solution 2a.

[0057] The test tank 2 includes a test tank body 20 having a front surface 20b with an opening 20a, and the test piece 1 is arranged adjacent to the front surface 20b of the test tank body 20 so as to cover the opening 20a, and a pair of resistance measurement terminals 6a may be sandwiched between the front surface 20b of the test tank body 20 and the other surface 1b of the test piece 1.

[0058] The measurement of the electrical resistance and the measurement of the anode current may be performed at different times.

[0059] The measurement method of this embodiment may be carried out using the above-mentioned measurement device. Details of the measurement method of this embodiment are the same as those described for the above-mentioned measurement device.

[0060] Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person skilled in the art to which the present invention pertains can conceive of various modifications and alterations within the scope of the technical ideas set forth in the claims, and it is understood that these also naturally fall within the technical scope of the present invention. [Example]

[0061] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0062] The inventors arranged a conventional corrosion sensor next to the measuring device for measuring the amount of corrosion and the amount of hydrogen penetration of a metal material (hereinafter, simply referred to as the "measuring device") described with reference to Figures 1 and 2. That is, the conventional hydrogen permeation cell of Figure 7 was replaced with the measuring device according to the embodiment of the present invention.

[0063] In the measurement device, a test piece 1 was placed so that one surface 1a was exposed to a corrosive environment and the other surface 1b formed part of the inner wall of a test tank 2 filled with an electrolyte solution 2a. A rectangular steel plate, as shown in Figure 2, was used as the test piece 1. The steel plate had dimensions of 100 mm in length, 30 mm in width, and 0.2 mm in thickness. The test tank body 20 had dimensions of 120 mm in length and 50 mm in width, and a rectangular opening 20a (86 mm in length and 26 mm in width) was provided in the center of the front surface 20b of the test tank body 20. A pair of resistance measurement terminals 6a was attached to the front surface 20b of the test tank body 20, and the test piece 1 was attached to the front surface 20b of the test tank body 20 above the pair of resistance measurement terminals 6a. The test piece 1 was positioned so that the center of the test piece 1 coincided with the center of the opening 20a. As shown in FIG. 2, the pair of resistance measurement terminals 6a were spaced apart in the longitudinal direction 1L of the test piece 1 and were positioned at the center of the test piece 1 in the lateral direction 1S of the test piece 1. The distance between the pair of resistance measurement terminals 6a in the longitudinal direction 1L of the test piece 1 was 90 mm. The corrosion monitoring area 10 had a vertical dimension of 90 mm, a horizontal dimension of 30 mm, and an area of ​​2700 mm. 2 The area of ​​the opening 20a is 2236 mm 2 ) is the area of ​​the corrosion monitoring area 10 (2700 mm 2 ) was 83%. 150 mL of electrolyte solution 2a was filled into test tank body 20. 0.1 M NaOH aqueous solution was used as electrolyte solution 2a.

[0064] The corrosion test piece used for the conventional corrosion sensor had the same shape as test piece 1 of the above-mentioned measuring device. The corrosion test piece was placed on a predetermined base and was not in contact with the electrolyte solution 2a.

[0065] The measurement device and the conventional corrosion sensor were then heated and cooled, and the temperatures of the test piece 1 and the electrolyte solution 2a of the measurement device, as well as the temperature of the corrosion test piece of the conventional corrosion sensor, were measured. The results are shown in Figure 6.

[0066] Figure 6 is a graph showing the temperature histories of the test piece 1, electrolyte solution 2a, and corrosion test piece when the corrosion amount and hydrogen intrusion amount measurement device for metal materials shown in Figure 1 and a conventional corrosion sensor are placed side by side. As shown in Figure 6, during heating, the test piece 1 of the measurement device rose in temperature more slowly than the corrosion test piece of the conventional corrosion sensor, and drew a curve similar to that of the electrolyte solution 2a. On the other hand, during cooling, the corrosion test piece of the corrosion sensor dropped in temperature more quickly than the test piece 1 of the measurement device, and the test piece 1 of the measurement device followed a temperature history similar to that of the electrolyte solution 2a, just as during heating. In other words, the test piece 1 placed in contact with the electrolyte solution 2a and the corrosion test piece not in contact with the electrolyte solution 2a differed significantly in their temperature response to environmental temperature changes, resulting in differences in their temperature histories.

[0067] The above explanation is for the case where a measuring device according to an embodiment of the present invention and a conventional corrosion sensor are arranged side by side. However, when a conventional hydrogen permeation cell is arranged side by side with a conventional corrosion sensor instead of the measuring device, as shown in Figure 7, it is clear that the temperature response to environmental temperature changes differs significantly between the hydrogen permeation test piece placed in contact with the electrolyte solution 2a and the corrosion test piece not in contact with the electrolyte solution 2a, resulting in a difference in temperature history between them.

[0068] In contrast, as shown in Figure 1, by measuring both the amount of corrosion and the amount of hydrogen that has penetrated from a test specimen 1 that is positioned so that one surface 1a is exposed to a corrosive environment and the other surface 1b forms part of the inner wall of a test tank 2 filled with an electrolyte solution 2a, the temperature difference between the test specimen 1 when measuring the amount of corrosion and the amount of hydrogen that has penetrated can be reduced compared to when the hydrogen permeation cell and corrosion sensor are positioned side by side, and the correlation between the corrosion rate and the hydrogen penetration rate can be grasped more accurately.

[0069] The invention described in this specification can also be described as follows. [1] a test piece made of a plate-shaped metal material, one surface of which is exposed to a corrosive environment and subjected to corrosion; a test tank having the other surface of the test piece as a part of its inner wall and filled with an electrolyte solution; a counter electrode and a reference electrode disposed inside the test chamber for detecting, as an anode current, the flux of hydrogen that penetrates the test piece from the one surface and diffuses to the other surface; a potential / current control device that measures the anode current flowing between the test piece and the counter electrode; a resistance meter that measures the electrical resistance of the test piece; a temperature measuring device for measuring the temperature of the electrolyte solution and / or the test piece; Equipped with The amount of corrosion of the test piece is determined based on the outputs of the resistance measuring device and the temperature measuring device, and the amount of hydrogen that has penetrated into the test piece is determined based on the output of the potential / current control device. A device for measuring the amount of corrosion and hydrogen penetration of metal materials. [2] the resistance meter has a pair of resistance measurement terminals connected to the test piece, the test piece has a corrosion monitoring region located between the pair of resistance measurement terminals; a majority of the other surface of the corrosion monitoring area is in contact with the electrolyte solution; 2. An apparatus for measuring the amount of corrosion and the amount of hydrogen penetration of the metal material described in paragraph 1. [3] The test chamber includes a test chamber body having a front surface with an opening; The test piece is disposed adjacent to the front surface of the test chamber body so as to cover the opening, the pair of resistance measurement terminals are sandwiched between the front surface of the test tank body and the other surface of the test piece; 3. An apparatus for measuring the amount of corrosion and the amount of hydrogen penetration of a metal material according to claim 2. [4] The measurement of the electrical resistance by the resistance meter and the measurement of the anode current by the potential / current control device are performed at different times. 4. An apparatus for measuring the amount of corrosion and the amount of absorbed hydrogen of a metal material according to any one of claims 1 to 3. [5] The device further includes a recording device that records the electrical resistance and temperature measured by the temperature measuring device and the resistance measuring device, and the anode current measured by the potential / current control device in chronological order. 5. An apparatus for measuring the amount of corrosion and the amount of absorbed hydrogen of a metal material according to any one of claims 1 to 4. [6] determining the amount of corrosion of a test piece from the electrical resistance of the test piece, which is placed so that one surface is exposed to a corrosive environment and the other surface forms part of the inner wall of a test tank filled with an electrolyte solution, and the temperature of the electrolyte solution and / or the test piece; and The amount of hydrogen that penetrates into the test piece is determined from the anode current due to the flux of hydrogen that penetrates into the test piece from the one surface and diffuses to the other surface. Including, Method for measuring the amount of corrosion and hydrogen penetration of metallic materials. [7] the test piece has a corrosion monitoring area located between a pair of resistance measurement terminals for measuring the electrical resistance, and a majority of the other surface of the corrosion monitoring area is in contact with the electrolyte solution; 7. A method for measuring the amount of corrosion and the amount of absorbed hydrogen of a metal material according to claim 6. [8] The test chamber includes a test chamber body having a front surface with an opening; The test piece is disposed adjacent to the front surface of the test chamber body so as to cover the opening, the pair of resistance measurement terminals are sandwiched between the front surface of the test tank body and the other surface of the test piece; 8. A method for measuring the amount of corrosion and the amount of absorbed hydrogen of a metal material according to claim 7. [9] The measurement of the electrical resistance and the measurement of the anode current are performed at different times. 9. A method for measuring the amount of corrosion and the amount of absorbed hydrogen of a metal material according to any one of claims 6 to 8. [Explanation of symbols]

[0070] 1: Test piece 1a: One side 1b: The other side 10: Corrosion monitoring area 2: Test tank 2a: Electrolyte solution 20: Test chamber body 20a: opening 20b:Front 3: Opposite 4:Reference electrode 5: Current control device 6: Resistance measuring instrument 6a: A pair of resistance measurement terminals 7: Temperature measuring instrument 8: Recording device

Claims

1. a test piece made of a plate-shaped metal material, one surface of which is exposed to a corrosive environment and subjected to corrosion; a test tank having the other surface of the test piece as a part of its inner wall and filled with an electrolyte solution; a counter electrode and a reference electrode disposed inside the test chamber for detecting, as an anode current, the flux of hydrogen that penetrates the test piece from the one surface and diffuses to the other surface; a potential / current control device that measures the anode current flowing between the test piece and the counter electrode; a resistance meter that measures the electrical resistance of the test piece; a temperature measuring device for measuring the temperature of the electrolyte solution and / or the test piece; Equipped with The amount of corrosion of the test piece is determined based on the outputs of the resistance measuring device and the temperature measuring device, and the amount of hydrogen that has penetrated into the test piece is determined based on the output of the potential / current control device. A device for measuring the amount of corrosion and hydrogen penetration of metal materials.

2. the resistance meter has a pair of resistance measurement terminals connected to the test piece, the test piece has a corrosion monitoring region located between the pair of resistance measurement terminals; a majority of the other surface of the corrosion monitoring area is in contact with the electrolyte solution; The apparatus for measuring the corrosion level and the amount of hydrogen penetration of a metallic material according to claim 1.

3. The test chamber includes a test chamber body having a front surface with an opening; The test piece is disposed adjacent to the front surface of the test chamber body so as to cover the opening, the pair of resistance measurement terminals are sandwiched between the front surface of the test tank body and the other surface of the test piece; The apparatus for measuring the amount of corrosion and the amount of hydrogen penetration of a metallic material according to claim 2.

4. the measurement of the electrical resistance by the resistance meter and the measurement of the anode current by the potential / current control device are performed at different times; The apparatus for measuring the amount of corrosion and the amount of absorbed hydrogen of a metal material according to any one of claims 1 to 3.

5. The apparatus further includes a recording device that records the electrical resistance and temperature measured by the temperature measuring device and the resistance measuring device, and the anode current measured by the potential / current control device in chronological order. The apparatus for measuring the amount of corrosion and the amount of absorbed hydrogen of a metal material according to any one of claims 1 to 3.

6. determining the amount of corrosion of a test piece from the electrical resistance of the test piece, which is placed so that one surface is exposed to a corrosive environment and the other surface forms part of the inner wall of a test tank filled with an electrolyte solution, and the temperature of the electrolyte solution and / or the test piece; and The amount of hydrogen that penetrates into the test piece is determined from the anode current due to the flux of hydrogen that penetrates into the test piece from the one surface and diffuses to the other surface. Including, Method for measuring the amount of corrosion and hydrogen penetration of metallic materials.

7. the test piece has a corrosion monitoring area located between a pair of resistance measurement terminals for measuring the electrical resistance, and a majority of the other surface of the corrosion monitoring area is in contact with the electrolyte solution; The method for measuring the amount of corrosion and the amount of absorbed hydrogen of a metallic material according to claim 6.

8. The test chamber includes a test chamber body having a front surface with an opening; The test piece is disposed adjacent to the front surface of the test chamber body so as to cover the opening, the pair of resistance measurement terminals are sandwiched between the front surface of the test tank body and the other surface of the test piece; The method for measuring the amount of corrosion and the amount of absorbed hydrogen of a metallic material according to claim 7.

9. The measurement of the electrical resistance and the measurement of the anode current are performed at different times. The method for measuring the amount of corrosion and the amount of absorbed hydrogen of a metallic material according to any one of claims 6 to 8.

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