Hydrogen penetration amount measurement device and hydrogen penetration amount measurement kit

Abstract

To provide a hydrogen penetration amount measurement device and a hydrogen penetration amount measurement system which can accurately measure the amount of hydrogen penetration into the inside of a metal material according to corrosion of the metal material over a long period.SOLUTION: A hydrogen penetration amount measurement device for measuring the amount of hydrogen penetrating into the inside of a metal material due to corrosion by an electrochemical hydrogen permeation method includes a plurality of electrochemical cells installed on one surface of the metal material. The electrolytic cells each include an electrolysis tank that holds an electrolytic solution so as to contact with the one surface of the metal material; electrodes which are provided penetrating the electrolysis tank in such a manner that their one ends are positioned inside the electrolysis tank and the other ends are positioned outside the electrolysis tank; covered wires connected to the other ends of the electrodes; and an insulation covering for covering a connection parts between the electrodes and the covered wires.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an apparatus for measuring the amount of hydrogen penetrating into a metal material due to corrosion by an electrochemical hydrogen permeation method and a kit for measuring the amount of hydrogen penetrating into a metal material due to corrosion by an electrochemical hydrogen permeation method.

Background Art

[0002] In recent years, from the viewpoints of energy conservation and resource conservation, the strength of steel materials used in industrial fields has been increasing. The steel sheets used in automobiles are also being strengthened, and the application of high-strength steel sheets with a tensile strength exceeding 1180 MPa is also being promoted.

[0003] However, as one of the problems of high-strength steel materials, the occurrence of "delayed fracture" is known. For example, it has often been reported that high-tensile bolts break in the use environment, and this breakage is caused by delayed fracture.

[0004] Delayed fracture is a phenomenon in which, when a metal material is subjected to a static load stress (a load stress equal to or less than the tensile strength) and a certain period of time has elapsed, sudden brittle fracture occurs with almost no plastic deformation on the surface. Delayed fracture is more likely to occur as the strength of the metal material increases, for example, in the case of steel materials. In particular, it is known that delayed fracture is likely to occur in high-strength steel materials with a tensile strength of 1180 MPa or more.

[0005] It is known that delayed fracture occurring in steel materials is caused by residual stress when the steel material is formed into a predetermined shape by processing such as press working and hydrogen embrittlement of the steel material at the concentration part of the residual stress.

[0006] In most cases, the hydrogen causing the above hydrogen embrittlement is hydrogen that has penetrated into the steel material from the external environment and diffused (penetrating hydrogen). It has been reported that the more the amount of hydrogen penetrating into the steel material, the more likely delayed fracture occurs. Therefore, in order to evaluate the delayed fracture characteristics of steel materials, it is important to evaluate the amount of hydrogen penetrating into the steel material with high accuracy.

[0007] Here, the hydrogen that penetrates from the external environment into the steel material is mainly the hydrogen generated along with the corrosion of the steel material. However, since the amount of hydrogen that penetrates into the steel material along with the corrosion of the steel material is extremely small, various techniques for measuring such a small amount of penetrating hydrogen have been proposed.

[0008] For example, Non-Patent Document 1 reports a method of continuously measuring, as an anodic current, the hydrogen that has penetrated from the surface of a steel plate exposed to an atmospheric corrosion environment on the opposite surface (detection surface) of the steel plate by means of an electrochemical hydrogen permeation method.

[0009] However, the anodic current measured by the electrochemical hydrogen permeation method includes, in addition to the hydrogen permeation current measured when hydrogen atoms that have penetrated through the steel plate are ionized on the detection surface, the passive state holding current of the metal formed on the detection surface side. Although it is known that the passive state holding current depends on temperature (Non-Patent Document 2), in the method described in Non-Patent Document 1, the temperature dependence is not considered, so the amount of penetrating hydrogen cannot be accurately evaluated.

[0010] Therefore, in Patent Document 1, a method for correcting the influence of the passive state holding current in the measurement of the amount of penetrating hydrogen by the electrochemical hydrogen permeation method has been proposed. Specifically, two or more measurement cells are installed for the same test piece, and a protective film is provided on the hydrogen penetration surface of one of the measurement cells to prevent the penetration of hydrogen, thereby serving as a reference cell for measuring the passive state holding current. By subtracting the passive state holding current measured by the reference cell from the anodic current measured by the normal measurement cell, the influence of the passive state holding current that varies with temperature is removed.

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Non-Patent Documents

[0012]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Non-Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0013] According to the method described in Patent Document 1, the measurement accuracy of the amount of hydrogen entering the interior of a steel material in an atmospheric corrosion environment can be improved. However, as a result of the inventors fabricating a cell having the structure described in FIG. 2 of Patent Document 1 and measuring the amount of hydrogen entering the steel material over a long period in various environments, there were cases where accurate measurement of the amount of hydrogen entering could not be performed from a certain time depending on the corrosion environment.

[0014] The present invention has been made in view of such circumstances, and an object thereof is to provide a hydrogen ingress amount measuring device and a hydrogen ingress amount measuring system capable of accurately measuring the amount of hydrogen entering the interior of a metal material over a long period as the metal material corrodes.

Means for Solving the Problems

[0015] In order to solve the above problems, the inventors fabricated a hydrogen ingress amount measuring system 100 shown in FIG. 5 by imitating the cell having the structure described in FIG. 2 of Patent Document 1, and measured the amount of hydrogen entering the steel material over a long period in various environments.

[0016] In this specification, a hydrogen ingress amount measurement kit 50 is a state in which an electrochemical cell or the like necessary for measurement is attached to a metal material 51 as a specimen. A hydrogen ingress amount measurement apparatus 1 is a part obtained by removing the metal material from the hydrogen ingress amount measurement kit 50. A hydrogen ingress amount measurement system 100 is a configuration in which an electrochemical measurement power supply PS is added to the hydrogen ingress amount measurement kit 50.

[0017] The hydrogen ingress amount measurement system 100 shown in FIG. 5 includes a metal material 51 as a specimen, a hydrogen ingress amount measurement apparatus 1 attached to one surface of the metal material 51, and an electrochemical measurement power supply PS connected to the hydrogen ingress amount measurement apparatus 1. A steel plate was used as the metal material 51. Also, a multi-potentiostat was used as the electrochemical measurement power supply PS.

[0018] A part of the other surface of the metal material 51 is covered with a protective layer 52 that prevents hydrogen ingress, and the portion covered with the protective layer 52 functions as a hydrogen non-ingress portion 53. On the other hand, the portion where the protective layer 52 is not provided functions as a hydrogen ingress portion 54. That is, since the metal material 51 is exposed to the surrounding environment in the hydrogen ingress portion 54, hydrogen is generated by corrosion and the generated hydrogen penetrates into the metal material 51.

[0019] The hydrogen ingress amount measurement apparatus 1 includes two electrochemical cells 2a and 2b. The electrochemical cell 2a is disposed on the opposite side of the hydrogen non-ingress portion 53, and the electrochemical cell 2b is disposed on the opposite side of the hydrogen ingress portion 54. With such an arrangement, the electrochemical cell 2a functions as a reference cell for measuring the passive holding current, and the electrochemical cell 2b functions as a cell for measuring the hydrogen ingress amount.

[0020] The electrochemical cells 2a and 2b each include an electrolytic cell 3, and an electrolytic solution 4 is held inside the electrolytic cell 3. The electrolytic solution 4 is in contact with one surface of the metal material 51.

[0021] Each of the electrochemical cells 2a and 2b includes two electrodes 5c and 5r provided through the wall surface of the electrolytic cell 3. The electrodes 5c and 5r are both arranged such that one end is located inside the electrolytic cell 3 and the other end is located outside the electrolytic cell 3. Therefore, one end side of the electrodes 5c and 5r is in contact with the electrolytic solution 4 inside the electrolytic cell 3.

[0022] On the other hand, the other ends of the electrodes 5c and 5r are connected to the coated wire 6, and the coated wire 6 is further connected to the electrochemical measurement power supply PS. The metal material 51 is also connected to the electrochemical measurement power supply PS by the coated wire 7. The measurement of the amount of hydrogen intrusion is performed in a three-electrode system with the metal material 51 as the working electrode, the electrode 5c as the counter electrode, and 5r as the reference electrode.

[0023] As a result of measuring the amount of hydrogen intrusion into the steel material in various environments using the above-described hydrogen intrusion amount measurement system 100, it was found that stable measurement could not be performed due to the wetting of the connection portion (contact point) 8 between the electrode 5 and the coated wire 6. This is presumably because, although only the electrochemical reaction on the surface of the metal material 51 should originally be the measurement target, the electrochemical reaction of the metal exposed at the connection portion 8 is also included in the measurement result.

[0024] The present invention has been completed based on the above findings, and the main configuration is as follows.

[0025] 1. A hydrogen intrusion amount measuring device that measures the amount of hydrogen intruding into the interior of a metal material due to corrosion by an electrochemical hydrogen permeation method, comprising a plurality of electrochemical cells installed on one surface of the metal material, wherein the electrochemical cell includes an electrolytic cell that holds an electrolytic solution inside so as to contact one surface of the metal material, an electrode provided through the electrolytic cell such that one end is located inside the electrolytic cell and the other end is located outside the electrolytic cell, a coated wire connected to the other end of the electrode, and an insulating coating that coats the connection portion between the electrode and the coated wire.

[0026] 2. The hydrogen ingress amount measuring device according to 1 above, wherein the insulating coating is made of resin.

[0027] 3. The hydrogen ingress amount measuring device according to 1 above, wherein the electrochemical cell further includes a sealing member that seals a penetrating portion through which the electrode penetrates the electrolytic cell.

[0028] 4. The hydrogen ingress amount measuring device according to 3 above, wherein the linear expansion coefficient of the sealing member is larger than the linear expansion coefficient of the material of the electrolytic cell.

[0029] 5. The insulating coating has a void portion inside, The hydrogen ingress amount measuring device according to any one of 1 to 4 above, wherein the electrode is arranged so as to penetrate the void portion.

[0030] 6. A hydrogen ingress amount measuring kit for measuring the amount of hydrogen that penetrates into a metal material due to corrosion by an electrochemical hydrogen permeation method, The metal material as a test specimen, A coated wire for energizing the metal material, A plurality of electrochemical cells provided on one surface of the metal material, On the other surface of the metal material, a hydrogen non-invasion portion covered with a protective layer that prevents hydrogen invasion and a hydrogen invasion portion where the protective layer is not provided are formed, One of the plurality of electrochemical cells is arranged on the opposite side of the hydrogen non-invasion portion, The rest of the plurality of electrochemical cells are arranged on the opposite side of the hydrogen invasion portion, The electrochemical cell is An electrolytic cell that holds an electrolytic solution inside so as to contact one surface of the metal material, An electrode provided through the electrolytic cell such that one end is inside the electrolytic cell and the other end is outside the electrolytic cell, A coated wire connected to the other end of the electrode, A hydrogen ingress amount measuring kit including an insulating coating that covers a connection portion between the electrode and the coated wire.

[0031] 7. The hydrogen ingress amount measurement kit according to item 6 above, wherein the insulating coating is made of resin.

[0032] 8. The hydrogen ingress amount measurement kit according to item 6 above, wherein the electrochemical cell further includes a sealing member that seals a penetrating portion through which the electrode penetrates the electrolytic cell.

[0033] 9. The hydrogen ingress amount measurement kit according to item 8 above, wherein the linear expansion coefficient of the sealing member is greater than the linear expansion coefficient of the material of the electrolytic cell.

[0034] 10. The insulating coating has a void portion inside, The hydrogen ingress amount measurement kit according to any one of items 6 to 9 above, wherein the electrode is disposed so as to penetrate the void portion.

Advantages of the Invention

[0035] According to the present invention, the amount of hydrogen ingress into the interior of a metal material due to corrosion of the metal material can be accurately measured over a long period of time.

Brief Description of the Drawings

[0036]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0037] Hereinafter, the present invention will be described with reference to the drawings. In each figure, corresponding parts are denoted by the same reference numerals. Note that the following description is about an example of a preferred embodiment of the present invention, and the present invention is not limited to the embodiments described below. Also, regarding points not particularly mentioned, it can be the same as the disclosure of Patent Document 1 above.

[0038] (First Embodiment) FIG. 1 is a schematic diagram showing the structure of the hydrogen intrusion amount measuring device 1 and the hydrogen intrusion amount measuring kit 50 in the first embodiment of the present invention.

[0039] The hydrogen intrusion amount measuring device 1 includes a plurality of electrochemical cells 2 installed on one surface (the lower surface in FIG. 1) of the metal material 51.

[0040] And the electrochemical cell 2 includes the following components. · An electrolytic cell 3 that holds an electrolytic solution 4 inside so as to be in contact with one surface (the lower surface in FIG. 1) of the metal material 51 · An electrode 5 provided so as to penetrate the electrolytic cell 3 such that one end is inside the electrolytic cell 3 and the other end is located outside the electrolytic cell 3 · A coated wire 6 connected to the other end of the electrode 5 · An insulating coating 9 that coats the connection portion 8 between the electrode 5 and the coated wire 6

[0041] Hereinafter, the details of each part will be described.

[0042] [Metal Material] The measuring device and measuring kit of the present invention are for measuring the amount of hydrogen that penetrates into the interior of a metallic material due to corrosion by means of the electrochemical hydrogen permeation method. That is, a metallic material is used as the test specimen. As the metallic material, any metallic material can be used without particular limitation, but usually, a material that causes delayed fracture may be used. Examples of materials that cause delayed fracture include steel, aluminum alloy, and nickel alloy. The steel may be, for example, carbon steel or stainless steel.

[0043] As described above, generally, the higher the strength of the steel material, the more likely it is to cause delayed fracture. Therefore, when using a steel material as the metallic material, it is preferable to use a high-strength steel with a high tensile strength as the steel material, and among them, it is preferable to use a high-strength steel with a tensile strength of 1180 MPa or more.

[0044] The metallic material may have a coating on at least a part of its surface. When the metallic material is in a plate shape, it may have a coating on at least one of its surfaces. The coating is not particularly limited, and any coating can be used. The coating may be a coating made of metal, a coating made of non-metal, or a coating made of both metal and non-metal. Examples of the non-metal include resin, ceramics, carbon, etc. The coating may be a plating layer or a coating film. Further, the coating may be a multilayer coating composed of a plurality of layers of the same or different types.

[0045] In addition, when the coating hinders the measurement, the coating existing at the position where the electrochemical cell is installed may be removed in advance, and then the electrochemical cell may be installed.

[0046] 1, an electrochemical cell 2 is placed on one surface of a metal material 51, and electrochemical measurements are performed using the electrochemical cell 2. It is preferable that the portion of one surface of the metal material 51 to which the electrochemical cell 2 is attached is provided with a layer (hereinafter referred to as a metal layer) made of a metal that has a large hydrogen diffusion constant and promotes an oxidation reaction of hydrogen. Examples of metals that constitute the metal layer include Pd, Pd alloys, and Ni. Examples of the Pd alloys include Pd-Ni alloys and Pd-Co alloys.

[0047] By covering with these metals, the oxidation reaction of the invaded hydrogen is promoted, and the sensitivity of the anode current due to the ionization of hydrogen can be increased. In addition, one of the electrochemical cells is used as a reference cell, and by providing the metal layer, the passive current in the reference cell can be reduced. Note that Pd has a larger hydrogen diffusion constant than Ni, and is also effective in reducing the temperature dependency of the passive current. For this reason, it is more preferable to use a Pd coating as the metal layer.

[0048] In addition, when the above-mentioned coating is present on the surface of the metal material, it is preferable to remove the coating present at the position where the electrochemical cell is to be installed to expose the surface of the metal material, and then form the metal layer at that position.

[0049] The thickness of the metal layer is not particularly limited, but is preferably 10 to 100 nm.

[0050] The metal layer is preferably a plated film formed by a plating method.

[0051] When forming a plating film of Pd or a Pd alloy as the metal layer, cathodic electrolysis may be performed in an aqueous solution (plating bath) containing palladium ions. Examples of the palladium ion source in the plating bath include [Pd(NH 3 ) 4 ]Cl 2 H 2Palladium compounds such as O can be used. When forming a Ni plating film, it may be cathodically electrolyzed in an arbitrary plating bath such as a Watts bath.

[0052] The metal layer may be a coating composed of a plurality of layers. For example, a Ni plating film formed on the surface of a metal material and a Pd plating film or a Pd alloy plating film formed on the Ni plating film can also be used.

[0053] The shape of the metal material as the test object is not particularly limited, and it may have any shape as long as it has one surface for attaching the electrochemical cell and the other surface through which hydrogen enters due to corrosion. Typically, it is preferable to use a plate-shaped metal material as shown in FIG. 1 as the test object.

[0054] The thickness of the metal material is not particularly limited, but if the metal material is excessively thick, the time lag between the change in the corrosion environment and the change in the measured hydrogen permeation current increases, and as a result, the relationship between the environmental factor and the amount of hydrogen entering may become unclear. Also, when the diffusion coefficient of hydrogen in the metal material is small, it is better to make the metal material 51 thinner. Further, from the viewpoint that accurate calculation of the surface hydrogen concentration cannot be performed when the hydrogen diffusion in the metal material is unsteady, the metal material is preferably thin. Therefore, the thickness of the metal material is preferably 1 mm or less, and more preferably 0.5 mm or less. On the other hand, if the metal material is excessively thin, perforation due to corrosion occurs in a short period of time, and measurement cannot be continued. Therefore, the thickness of the metal material is preferably 0.2 mm or more.

[0055] (Hydrogen non-invasion part) The hydrogen intrusion amount measuring device of the present invention includes a plurality of electrochemical cells, one of which can be used as a reference cell and the other cells can be used as cells for measuring the hydrogen intrusion amount. By measuring the passive holding current in the reference cell and subtracting the passive holding current from the current measured in the cell for measuring the hydrogen intrusion amount, it becomes possible to monitor the hydrogen intrusion amount without being affected by the temperature dependence of the passive holding current.

[0056] In order to measure the passive holding current with the reference cell in this way, it is necessary to provide a hydrogen non-invading portion 53 covered by a protective layer 52 that prevents the intrusion of hydrogen on a part of the other surface of the metal material 51. In the hydrogen non-invading portion 53, since the protective layer 52 exists, the metal material 51 is not directly exposed to the corrosive environment. Therefore, in the electrochemical cell 2a, i.e., the reference cell, arranged on the opposite surface of the hydrogen non-invading portion, the current caused by the invading hydrogen is not measured, and only the passive holding current is measured.

[0057] Note that if the area of the hydrogen non-invading portion 53 is excessively small, the current measured by the reference cell may include a component caused by the invading hydrogen. Therefore, the area of the hydrogen non-invading portion 53 is preferably larger than the measurement area of the electrochemical cell 2a (reference cell) arranged on the opposite surface of the hydrogen non-invading portion. Here, the area of the hydrogen non-invading portion 53 is the area covered by the protective layer 52. Also, the measurement area of the electrochemical cell 2a is the area of the portion of the surface of the metal material 51 where the electrolytic solution 4 in the electrolytic cell 3 of the electrochemical cell 2a is in contact. Usually, the measurement area is equal to the area of the opening of the electrolytic cell 3 of the electrochemical cell 2a.

[0058] The protective layer 52 is not particularly limited as long as it can block the corrosive environment, and any layer can be used. Examples of the protective layer 52 include stainless steel foil pasted on the surface of the metal material 51 with an organic adhesive, anticorrosive coating, etc.

[0059] (Hydrogen invasion part) On the other hand, the portion of the other surface of the metal material 51 where the protective layer 52 is not provided functions as a hydrogen invasion portion 54. That is, since the hydrogen invasion portion 54 is not protected by the protective layer, it is directly exposed to the corrosive environment. Therefore, corrosion of the metal material 51 progresses on the surface of the hydrogen invasion portion 54, and the hydrogen generated accordingly invades into the metal material 51. The invaded hydrogen diffuses inside the metal material 51 and reaches the opposite surface of the metal material 51, and is detected by the electrochemical cell 2b, i.e., the cell for measuring the amount of invaded hydrogen, arranged on the opposite surface of the hydrogen invasion portion 54.

[0060] Coated wire When measuring the amount of hydrogen intrusion using the device of the present invention, electrochemical measurement is performed with the metal material 51 as the working electrode. Therefore, when using the hydrogen intrusion amount measuring device of the present invention, an electric current is passed through the metal material 51 through the coated wire 7. Further, the hydrogen intrusion amount measuring kit 50 of the present invention includes a coated wire 7 for passing an electric current through the metal material 51. When performing the measurement, the coated wire 7 may be connected to the terminal for the working electrode of the power supply PS for electrochemical measurement.

[0061] The coated wire 7 is not particularly limited, and any wire can be used. Typically, the same wire as the coated wire 6 connected to the electrode described later can be used.

[0062] [Electrochemical cell The hydrogen intrusion amount measuring device 1 and the hydrogen intrusion amount measuring kit 50 of the present invention include a plurality of electrochemical cells 2. One of the plurality of electrochemical cells 2 is used as a reference cell, and the rest are used as cells for measuring the amount of hydrogen intrusion.

[0063] The number of electrochemical cells 2 may be any number of 2 or more. In FIG. 1, the case where the number of electrochemical cells 2 is 2 is shown as an example, but the number of electrochemical cells 2 may be 2 or more. In other words, the number of cells for measuring the amount of hydrogen intrusion may be 1 or 2 or more. When there are a plurality of cells for measuring the amount of hydrogen intrusion, the amount of hydrogen intrusion at a plurality of positions of the metal material 51 can be measured simultaneously. However, if the number of electrochemical cells 2 is too large, the device structure becomes complicated and the cost increases. Therefore, the number of electrochemical cells 2 is preferably 10 or less, and more preferably 5 or less.

[0064] Next, the structure of the electrochemical cell 2 will be described. Note that the structures of the reference cell and the cell for measuring the amount of hydrogen intrusion may be basically the same.

[0065] (Electrolytic cell) The electrochemical cell 2 includes an electrolytic cell 3. As the electrolytic cell 3, any type can be used as long as it can accommodate the electrolytic solution 4 and bring the electrolytic solution 4 into contact with the surface of the metal material 51. Typically, as shown in FIG. 1, the electrolytic cell 3 has an opening for bringing the electrolytic solution 4 into contact with the metal material 51.

[0066] The material of the electrolytic cell 3 is not particularly limited, but from the viewpoints of durability, workability, ease of operation, chemical resistance to the electrolytic solution, etc., it is preferably made of resin. Also, from the viewpoint of being able to visually confirm the state of the electrolytic solution in the electrolytic cell 3, the electrolytic cell 3 is preferably transparent. From the above viewpoints, the electrolytic cell 3 is more preferably made of acrylic resin.

[0067] (Electrolytic solution) The electrolytic solution 4 is not particularly limited, and any electrolytic solution can be used. From the viewpoint of maintaining the surface of the metal material 51 in a passive state during measurement, it is preferable that the pH of the electrolytic solution 4 is 9 or more. On the other hand, if it is strongly alkaline with a pH higher than 13, when it leaks due to an accident, the damage to the environment is large. Therefore, it is preferable that the pH of the electrolytic solution 4 is 13 or less.

[0068] The composition of the electrolytic solution is not particularly limited and can be any composition. From the viewpoint of ensuring the passivation state of the surface of the metal material 51, for example, an aqueous NaOH solution of about 0.1 to 0.5 M (M = mol / L) is preferably used.

[0069] The electrolytic solution may be in a liquid state, but from the viewpoints of preventing leakage of the electrolytic solution and ease of handling, it is also preferable to use a gel electrolyte. To make the electrolytic solution gel-like, an arbitrary gelling agent may be added to the electrolytic solution.

[0070] (Electrode) Each electrochemical cell 2 includes at least one electrode 5. When measuring the amount of hydrogen intrusion by a two-electrode method, it is sufficient if the electrochemical cell 2 includes one electrode 5. In this case, the metal material 51 serves as the working electrode, and the electrode 5 of the electrochemical cell 2 serves as the counter electrode.

[0071] However, from the viewpoint of more accurately controlling the potential of the metal material 51, it is preferable to use a three - electrode system rather than a two - electrode system. When measuring the amount of hydrogen intrusion with a three - electrode system, as shown in FIG. 1, the electrochemical cell 2 may be provided with two electrodes 5c and 5r. In this case, the metal material 51 is used as the working electrode, the electrode 5c is used as the counter electrode, and the electrode 5r is used as the reference electrode.

[0072] · Counter electrode The material of the electrode 5c used as the counter electrode is not particularly limited as long as it can measure the anodic current, but typically it is preferable to use a metal electrode. The metal is not particularly limited, but it is preferable to use an inert metal so as not to inhibit the ionization reaction of hydrogen atoms. Examples of the inert metal include platinum, gold, ruthenium, rhodium, palladium, iridium, and their alloys. Among them, platinum and gold are very stable in the electrolyte and have high conductivity, so they are preferably used as the counter electrode. An electrode in which the inert metal is plated on the surface of a substrate such as titanium can also be used.

[0073] · Reference electrode The reference electrode is an electrode that serves as a potential reference when measuring the anodic current and is also referred to as a reference electrode. The material of the electrode 5r used as the reference electrode is not particularly limited, but typically it is preferable to use a metal electrode, and more preferably it is iridium (Ir) or tungsten (W). This is because Ir and W can form an oxide film on the surface in the electrolyte and can obtain a long - term stable potential. An electrode in which Ir or W is plated on the surface of a substrate such as titanium can also be used.

[0074] The shape of the electrode 5 is not particularly limited in either the case of the counter electrode or the reference electrode and can be any shape. Typically, it is preferably rod - shaped or wire - shaped.

[0075] The electrode 5 is installed so as to penetrate the electrolytic cell 3 such that one end is inside the electrolytic cell 3 and the other end is outside the electrolytic cell 3.

[0076] When measuring the amount of hydrogen intrusion, the anodic current may be measured using the above-mentioned electrochemical cell. The polarization conditions for measuring the anodic current are not particularly limited, but the potential may be such that the ionization reaction of hydrogen occurs sufficiently on the surface of the metal material 51 and the passivation state of the surface of the metal material 51 can be maintained. Generally, in an aqueous solution of 1M NaOH as the electrolyte, polarization conditions of -0.1 to 0.3V vs. SCE are widely used (Non-Patent Document 3). Here, SCE refers to a saturated calomel electrode, and the potential of this SCE with respect to the standard hydrogen electrode (SHE) is +0.244V (vs SHE, 25°C). Also, when using SSE, it can be measured at 0V (Non-Patent Document 4).

[0077] (Coated wire) The other end of the electrode 5, that is, the end located outside the electrolytic cell 3, is connected to the coated wire 6. The coated wire 6 is for connecting the electrode 5 to the electrochemical measurement power supply PS.

[0078] The coated wire 6 is not particularly limited, and any one can be used. Typically, a metal wire coated with an insulating material such as resin can be used as the coated wire 6. The metal wire is preferably a wire made of a metal with low electrical resistance such as silver or copper.

[0079] The connection between the electrode 5 and the coated wire 6 can be made by any method. Typically, soldering can be used. In addition, when the material of the electrode 5 is difficult to solder, another metal that is easy to solder may be interposed between the electrode 5 and the coated wire 6.

[0080] (Insulating coating) In the present invention, it is important to provide an insulating coating 9 so as to cover the connection portion 8 between the electrode 5 and the coated wire 6. In the conventional apparatus, as shown in FIG. 5, since there is no insulating coating, the connection portion 8 between the electrode 5 and the coated wire 6 is exposed. Therefore, for example, when measurement is performed outdoors, the connection portion 8 may get wet due to moisture or rainwater generated by dew condensation. Further, when the electrolytic solution 4 leaks from the portion where the electrode 5 penetrates the electrolytic cell 3, the connection portion 8 comes into contact with the electrolytic solution 4. Then, a redox reaction occurs on the surface of the connection portion 8, and the current thereof is included in the measured current, making it difficult to accurately measure the amount of hydrogen intrusion. On the other hand, in the present invention, since the connection portion 8 is covered with the insulating coating 9, it is possible to prevent the connection portion 8 from coming into contact with moisture, and as a result, it is possible to stably measure the amount of hydrogen intrusion.

[0081] Here, it is common for the measurement of the amount of hydrogen intrusion to be carried out over a long period. According to the study by the present inventors, when the electrochemical cell is exposed to a temperature difference exceeding 20 °C during such a long-term measurement, a fine gap is generated between the electrolytic cell 3 and the electrode 5, and the electrolytic solution 4 leaks due to capillary action. However, by providing the insulating coating 9 as described above, it is possible to stably measure the amount of hydrogen intrusion even during long-term measurement.

[0082] As the insulating coating 9, any insulating material can be used, but it is preferable to use a resin, and among them, it is preferable to use an epoxy resin. This is because the epoxy resin has a small shrinkage during solidification, and as a result, it is difficult to generate a gap between the connection portion 8 and the insulating coating 9.

[0083] The insulating coating 9 only needs to cover at least the connection portion 8 between the electrode 5 and the coated wire 6, but as shown in FIG. 1, it may cover a wider range.

[0084] (Second Embodiment) FIG. 2 is a schematic diagram showing the structure of the hydrogen intrusion amount measuring apparatus 1 and the hydrogen intrusion amount measuring kit 50 according to the second embodiment of the present invention. Note that parts not particularly mentioned may be the same as those in the first embodiment above.

[0085] In this embodiment, the electrochemical cell 2 further includes a seal member 10. The seal member 10 may be provided so as to seal the through-hole through which the electrode 5 penetrates the electrolytic cell 3. In other words, the seal member 10 may be provided between the electrode 5 and the electrolytic cell 3 in the through-hole. By providing the seal member 10 in this way, it is possible to prevent the electrolytic solution from leaking from the gap of the through-hole. By using the seal member 10 in combination with the insulating coating 9 described in the first embodiment, it is possible to more stably measure the amount of hydrogen intrusion over a long period of time.

[0086] As the material of the seal member, it is preferable to use a material having a coefficient of linear expansion larger than that of the material of the electrolytic cell 3. For example, when the electrolytic cell 3 is made of an acrylic resin, since the coefficient of linear expansion of the acrylic resin is about 5×10 -5 / °C, the coefficient of linear expansion of the material constituting the seal member 10 is preferably higher than 5×10 -5 / °C. Examples of the seal member 10 that can be preferably used include rubber. Examples of the rubber include silicone rubber (coefficient of linear expansion: 30×10 -5 / °C), ethylene propylene rubber (coefficient of linear expansion: 24×10 -5 / °C), butyl rubber (coefficient of linear expansion: 18×10 -5 / °C), and the like.

[0087] The seal member 10 preferably has water repellency. This is because it can further prevent the penetration of the electrolytic solution 4 between the seal member 10 and the electrode 5. The water repellency can be improved by providing fine irregularities on the surface of the seal member 10. The provision of the irregularities is not particularly limited and can be performed by any method. For example, fine irregularities may be provided on the surface of the seal member 10 by methods such as blasting or etching. Also, irregularities may be formed when the seal member 10 is molded. For example, if the seal member 10 is molded using a mold having irregularities on its inner surface, irregularities can be formed on the surface of the seal member 10.

[0088] The degree of water repellency is not particularly limited, but typically, the contact angle on the surface of the seal member 10 is preferably 90° or more. Since it is considered that the higher the water repellency, the higher the effect of preventing the penetration of the electrolytic solution 4, the contact angle is more preferably 100° or more, and even more preferably 120° or more. As the contact angle, the contact angle with respect to water can be used, but the contact angle with respect to the electrolytic solution used for actual measurement may also be used.

[0089] The installation method of the seal member 10 is not particularly limited, and it may be installed by any method. For example, a through-hole for passing the electrode 5 is provided in the wall surface of the electrolytic cell 3, and the seal member 10 can be installed so as to fill the gap between the electrode 5 and the electrolytic cell 3 when the electrode 5 is installed in the through-hole. The diameter of the through-hole is preferably 10 to 20 times the diameter of the electrode. This is because if the diameter of the through-hole is less than 10 times the diameter of the electrode, it becomes difficult to fill the gap with the seal member. On the other hand, if the diameter of the through-hole exceeds 20 times the diameter of the electrode, it will interfere with other components.

[0090] The size of the seal member is not particularly limited, and any size that can block the through-hole may be used. The size of the seal member may be adjusted according to the elastic modulus of the material used for the seal material.

[0091] The shape of the seal member is also not particularly limited, and any shape that can block the through-hole may be used. For example, a columnar or frustum-shaped seal member can also be used with the electrode passing through it. Also, a seal member can be formed by filling the through-hole with an amorphous (paste-like) material such as a caulking agent (sealing agent). As the caulking agent, for example, those made of silicone resin (silicone sealant), acrylic resin, epoxy resin, etc. can be used.

[0092] (Third Embodiment) In the third embodiment of the present invention, a void portion 11 is provided inside the insulation coating 9, and the electrode 5 is disposed so as to penetrate the void portion 11. Note that, for parts not particularly mentioned, the same applies as in the first embodiment or the second embodiment.

[0093] FIG. 3 is a schematic diagram showing an example of the arrangement of the void portion in this embodiment. The void portion 11 is a cavity provided inside the insulation coating 9. When the void portion 11 is provided as shown in FIG. 3, even if the electrolytic solution 4 leaks from the portion where the electrode 5 penetrates the electrolytic cell 3, it is trapped by the void portion 11, so that it is possible to prevent the leaked electrolytic solution 4 from reaching the connection portion 8 between the electrode 5 and the coated wire 6. Therefore, by providing the insulation coating 9 as described in the first embodiment and further providing the void portion 11 in the insulation coating 9, it is possible to more stably measure the amount of hydrogen intrusion over a long period of time.

[0094] The number of the void portions 11 is not particularly limited, and the number of void portions per electrochemical cell (that is, per insulation coating) may be one or two or more.

[0095] For example, as shown in FIG. 3(a), a structure in which one void portion 11 is penetrated by two electrodes 5c and 5r may be used. Also, as shown in FIG. 3(b), two void portions 11 may be provided inside the insulation coating 9, and the electrodes 5c and 5r may have a structure in which they penetrate different void portions 11, respectively. Further, a structure in which one electrode 5 penetrates a plurality of void portions 11 may be used.

[0096] In any case, it is important that the electrode 5 is disposed so as to penetrate the void portion 11. In other words, the void portion 11 is located on the side of the electrolytic cell 3 rather than the connection portion 8 between the electrode 5 and the coated wire. This is because it is necessary to trap the leaked electrolytic solution 4 in the void portion 11 before it reaches the connection portion 8.

[0097] In addition, although the sealing member is not essential in the present embodiment, it is preferable to further provide a sealing member. That is, the gap portion 11 can also be adopted in the second embodiment described above.

Examples

[0098] Hereinafter, the present invention will be described more specifically by way of examples, but the present invention is not limited to these examples.

[0099] (Example 1) In order to confirm the effects of providing the insulating coating and the gap portion, the following test was conducted to evaluate the life of the hydrogen intrusion amount measuring device.

[0100] The amount of hydrogen intrusion was measured using the device shown in FIG. 1. The measurement conditions were as shown in Table 1. As the metal material 51 (specimen), mild steel or high-strength steel plate was used, and the dimensions of the metal material 51 were width 50 mm × length 50 mm × thickness 0.5 mm. On one surface of the metal material 51, Pd plating with a thickness of about 100 nm was applied, and the electrochemical cell 2 was installed on that surface. On the other surface of the metal material 51, a hydrogen non-intrusion portion covered with a protective layer 52 that prevents hydrogen intrusion and a hydrogen intrusion portion where the protective layer 52 was not provided were provided.

[0101] Other conditions were as follows. ·Electrolytic cell 3: Made of acrylic resin ·Electrolyte 4: 0.1M NaOH aqueous solution (pH 13) ·Counter electrode 5c: Ir wire (0.5 mmφ, length 20 mm) ·Reference electrode 5r: Pt wire (0.5 mmφ, length 20 mm) ·Insulating coating 9: Epoxy resin ·Protective layer 52: Sealing agent (manufactured by Shin-Etsu Chemical Co., Ltd.) ·Power supply PS: Multi-potentiostat (three-electrode type)

[0102] Under the above conditions, the anodes of the electrochemical cell 2a (reference cell) and the electrochemical cell 2b (cell for measuring the amount of hydrogen permeation) were polarized so that the potential became 0 V vs. SSE in each of them. When measuring the hydrogen permeation current, the correction of the passivation holding current was carried out according to the method disclosed in Patent Document 1.

[0103] For comparison, the same measurement was carried out with the configuration of FIG. 1 without an insulating coating. Also, in some inventive examples, as shown in FIG. 3(b), a void portion 11 was further provided inside the insulating coating 9. The size of each void portion 11 was about 5 mm in diameter × about 1 mm in thickness.

[0104] The life of the apparatus for measuring the amount of hydrogen permeation was judged by the following criteria after installing the apparatus for measuring the amount of hydrogen permeation in an atmospheric exposure environment. The results are also shown in Table 1. Since a positive current is measured when the measurement is being carried out normally, it was judged that the life was reached when a negative current was measured. As the atmospheric exposure environment, a place where a temperature change of 20°C or more was observed throughout the year was selected. <Judgment Criteria> A: Life is 2 years or more B: Life is more than 1 year and less than 2 years C: Life is less than 1 year As shown in Table 1, in the inventive examples with an insulating coating, the life was 1 year or more, and in the inventive examples with a void portion provided, the life was 2 years or more.

[0105] (Example 2) Next, the following test was carried out to confirm the effect of providing a sealing member.

[0106] Using an apparatus for measuring the amount of hydrogen permeation equipped with three electrochemical cells, the hydrogen permeation current was measured. At that time, one of the three electrochemical cells was used as a reference cell for correcting the passivation holding current. The correction was carried out by the method disclosed in Patent Document 1. The remaining two electrochemical cells were used as cells for measuring the amount of hydrogen permeation.

[0107] Of the two cells for measuring the amount of hydrogen ingress, a sealing member was installed in one of them. Specifically, a through-hole with a diameter of 7 mm was provided in the electrolytic cell. After passing an electrode through it, a sealing member made of silicone rubber with a diameter of 7.5 mm was filled in it. For comparison, no sealing member was installed in the other cell for measuring the amount of hydrogen ingress. Other conditions were as follows. · Electrode: diameter 0.5 mm (common) · Through-hole with sealing member: diameter 7 mm, · Through-hole without sealing member: diameter 0.5 mm

[0108] As the metal material, a mild steel plate with a width of 50 mm × a length of 50 mm × a thickness of 0.5 mm was used. For other conditions, it was the same as in Example 1 above.

[0109] The hydrogen ingress measurement device was exposed to the outdoor environment, and the anode current density was measured. Fig. 4 is a graph showing a part of the change over time of the anode current density in the two cells for measuring the amount of hydrogen ingress. For some period after the start of the measurement, the anode current densities in the two cells were almost the same (the graphs overlap in Fig. 4).

[0110] However, it can be seen that the anode current density a in the cell without the sealing member suddenly became negative from mid-May and repeated discontinuous increases and decreases, making it impossible to measure normally. The life of this cell was about 1.5 years. On the other hand, the anode current density b in the cell with the sealing member showed increases and decreases corresponding to the changes in the exposure environment even after 2 years, and it was found that normal measurement could be carried out even in a long-term test exceeding 2 years.

[0111]

Table 1

Explanation of symbols

[0112] 1 Hydrogen ingress measurement device 2 Electrochemical cell 2a Reference cell 2b Cell for Measuring Hydrogen Ingress 3 Electrolytic Cell 4 Electrolyte 5 Electrode 5c Counter Electrode 5r Reference Electrode 6 Coated Wire 7 Coated Wire 8 Connection Part 9 Insulating Coating 10 Sealing Member 50 Kit for Measuring Ingress Hydrogen Amount 51 Metal Material 52 Protective Layer 53 Hydrogen Non-Ingress Part 54 Hydrogen Ingress Part 100 System for Measuring Ingress Hydrogen Amount PS Power Supply for Electrochemical Measurement (Potentiostat)

Claims

1. An apparatus for measuring the amount of hydrogen invading into a metal material by corrosion, which measures the amount of hydrogen invading into the metal material by an electrochemical hydrogen permeation method, comprising: a plurality of electrochemical cells installed on one surface of the metal material; wherein the electrochemical cell: an electrolytic cell that holds an electrolyte inside so as to contact one surface of the metal material; an electrode provided to penetrate the electrolytic cell such that one end is inside the electrolytic cell and the other end is outside the electrolytic cell; a coated wire connected to the other end of the electrode; an insulating coating that coats a connection portion between the electrode and the coated wire, the apparatus for measuring the amount of hydrogen invading.

2. The apparatus for measuring the amount of hydrogen invading according to claim 1, wherein the insulating coating is made of resin.

3. The apparatus for measuring the amount of hydrogen invading according to claim 1, wherein the electrochemical cell further comprises a sealing member that seals a penetrating portion through which the electrode penetrates the electrolytic cell.

4. The apparatus for measuring the amount of hydrogen invading according to claim 3, wherein a linear expansion coefficient of the sealing member is larger than a linear expansion coefficient of a material of the electrolytic cell.

5. The insulating coating has a void portion inside, and the electrode is disposed so as to penetrate the void portion, the apparatus for measuring the amount of hydrogen invading according to any one of claims 1 to 4.

6. A kit for measuring the amount of hydrogen invading into a metal material by corrosion, which measures the amount of hydrogen invading into the metal material by an electrochemical hydrogen permeation method, comprising: the metal material as a test specimen; a coated wire for energizing the metal material; a plurality of electrochemical cells installed on one surface of the metal material; on the other surface of the metal material, a hydrogen non-invading portion covered with a protective layer that prevents hydrogen invasion and a hydrogen invading portion where the protective layer is not provided are formed; one of the plurality of electrochemical cells is disposed on the opposite surface of the hydrogen non-invading portion; the rest of the plurality of electrochemical cells are disposed on the opposite surface of the hydrogen invading portion; wherein the electrochemical cell: an electrolytic cell that holds an electrolyte inside so as to contact one surface of the metal material; an electrode provided to penetrate the electrolytic cell such that one end is inside the electrolytic cell and the other end is outside the electrolytic cell; a coated wire connected to the other end of the electrode; an insulating coating that coats a connection portion between the electrode and the coated wire, the kit for measuring the amount of hydrogen invading.

7. The kit for measuring the amount of hydrogen invading according to claim 6, wherein the insulating coating is made of resin.

8. The hydrogen ingress measurement kit according to claim 6, wherein the electrochemical cell further comprises a sealing member that seals a through portion through which the electrode penetrates the electrolytic cell.

9. The hydrogen ingress measurement kit according to claim 8, wherein the linear expansion coefficient of the sealing member is greater than the linear expansion coefficient of the material of the electrolytic cell.

10. The insulating coating has a void portion inside, The hydrogen ingress measurement kit according to any one of claims 6 to 9, wherein the electrode is disposed so as to penetrate the void portion.

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