Specimen and method for measuring amount of hydrogen intrusion

Abstract

A specimen (100) comprises a metal plate (101), a metal layer (102), a material piece (103), and a support frame (105). The metal layer (102) is formed on a first surface (111) of the metal plate (101). The material piece (103) has, for example, a plate shape, and is disposed substantially parallel to and separated from the metal plate (101) on the side of a second surface (112) on the opposite side of the first surface (111) of the metal plate (101). Additionally, a through-hole (104) is formed in the center of the material piece (103). The support frame (105) is annular. The support frame (105) supports the material piece (103) above the metal plate (101) at an annular position centered on the position of the through-hole (104). A container having the second surface (112) of the metal plate (101) as the bottom surface is formed by the metal plate (101), the material piece (103), and the support frame (105).

Description

Test specimen and hydrogen penetration measurement method

[0001] The present invention relates to a test piece and a method for measuring the amount of hydrogen penetration.

[0002] Metal structures installed outdoors, such as infrastructure facilities, are at risk of fracture due to hydrogen embrittlement when hydrogen generated by corrosion reactions penetrates into the metal. In real-world environments, metals placed in crevice corrosion environments, such as bolts and rebar in concrete utility poles, can sometimes fracture due to hydrogen embrittlement. The more hydrogen that penetrates into the metal due to corrosion reactions, the higher the probability of fracture. Therefore, quantifying where and how much hydrogen penetrates into steel in a crevice corrosion environment is important for assessing the risk of hydrogen embrittlement.

[0003] Meanwhile, hydrogen permeation testing is a technique for continuously measuring the amount of hydrogen that penetrates a metal test piece prepared as a sample (Non-Patent Document 1). In this hydrogen permeation test, one side of the metal test piece is designated the "hydrogen penetration side," and the opposite side is designated the "hydrogen detection side." When hydrogen penetrates the metal from the penetration side, it diffuses inside the metal test piece and reaches the detection side, where it is electrochemically forcibly ionized. The amount of hydrogen that has penetrated the metal is determined by measuring the electrons released during ionization as a current.

[0004] Toru Mizunare, "Measurement of Hydrogen Penetration and Permeation into Steel by Electrochemical Method," Materials and Environment, Vol. 63, No. 1, pp. 3-9, 2014.

[0005] However, with conventional technology, hydrogen is detected uniformly across the entire hydrogen detection side, so even if hydrogen penetrates unevenly into the steel, such as in a crevice corrosion environment where hydrogen embrittlement is a concern in actual environments, the hydrogen is detected in an averaged state. However, because the risk of hydrogen embrittlement increases the higher the density of the penetrated hydrogen, it is important to understand the unevenness of hydrogen penetration, i.e., where and how much hydrogen has penetrated.

[0006] The present invention has been made to solve the above problems, and has as its object to make it possible to grasp where and how much hydrogen has penetrated.

[0007] The specimen according to the present invention comprises a metal plate, a metal layer made of Pd or Ni formed on a first surface of the metal plate, a piece of material arranged approximately parallel to and spaced apart from the metal plate on the second surface opposite the first surface of the metal plate, the piece having a through hole formed in the center, and a ring-shaped support frame that supports the piece of material on the metal plate at a ring-shaped position centered on the position of the through hole, and the metal plate, the piece of material, and the support frame form a container whose bottom is the second surface of the metal plate.

[0008] The method for measuring hydrogen penetration amount according to the present invention uses a specimen comprising: a metal plate; a metal layer made of Pd or Ni formed on a first surface of the metal plate; a plate-shaped material piece arranged substantially parallel to and spaced from the metal plate on a second surface opposite the first surface of the metal plate, the plate-shaped material piece having a through hole formed in its center; and an annular support frame supporting the material piece on the metal plate at a circular portion centered on the position of the through hole, the metal plate, the material piece, and the support frame forming a container with the second surface of the metal plate as its bottom. In each of a circular first region in the center of the region surrounded by the support frame, a circular second region surrounding the first region, and a circular third region surrounding the second region, the metal plate is used as a working electrode, and the amount of hydrogen penetrated from the first surface of the metal plate is measured in each of the first, second, and third regions by constant-potential polarization measurement using a reference electrode and a counter electrode in each of the electrolyte solutions individually brought into contact with the metal layer.

[0009] As described above, according to the present invention, a material piece having a through hole formed in the center and spaced apart from the metal plate is arranged approximately parallel to the metal plate, and the material piece is supported on the metal plate by a support frame arranged in a ring-shaped position centered on the position of the through hole, and a container is formed by the metal plate, material piece, and support frame, so that it is possible to determine where and how much hydrogen has penetrated into the metal plate.

[0010] Fig. 1 is a cross-sectional view showing the structure of a specimen 100 according to an embodiment of the present invention. Fig. 2 is a diagram showing the structure of a measurement system for carrying out a method for measuring the amount of absorbed hydrogen according to an embodiment of the present invention. Fig. 3 is an explanatory diagram for explaining the method for measuring the amount of absorbed hydrogen using the specimen 100 according to an embodiment of the present invention.

[0011] A specimen 100 according to an embodiment of the present invention will be described below with reference to Fig. 1. The specimen 100 includes a metal plate 101, a metal layer 102, a material piece 103, and a support frame 105.

[0012] The metal layer 102 is made of Pd or Ni and is formed on the first surface 111 of the metal plate 101. For example, the metal layer 102 can be a plated layer. The material piece 103 is, for example, in the shape of a plate and is arranged substantially parallel to and spaced apart from the metal plate 101 on the second surface 112 side of the metal plate 101 opposite the first surface 111. The material piece 103 also has a through hole 104 formed in its center. The material piece 103 can be made of a material suitable for the environment to be simulated, such as plastic such as acrylic, concrete, or metal.

[0013] The support frame 105 is annular (e.g., circular). The support frame 105 supports the material piece 103 on the metal plate 101 at an annular position centered on the position of the through hole 104. The support frame 105 may be, for example, an O-ring made of rubber (elastomer). The metal plate 101, the material piece 103, and the support frame 105 form a container whose bottom is the second surface 112 of the metal plate 101.

[0014] The specimen 100 is used to measure the amount of hydrogen that penetrates into the metal plate 101 after being introduced into the vessel through the through hole 104. The material piece 103 simulates a crevice corrosion environment.

[0015] Next, a hydrogen penetration amount measurement method according to an embodiment of the present invention will be described. First, a measurement system for carrying out the hydrogen penetration amount measurement method will be described with reference to Figs. 2 and 3. Fig. 3(a) is a plan view of the metal plate 101 of the specimen 100 placed in the measurement system, as viewed from above, which is the normal direction to the plane of the metal plate 101. Fig. 3(b) is a cross-sectional view of the specimen 100. Fig. 3(c) is a plan view of the measurement system in which the specimen 100 is placed, as viewed from above.

[0016] This measurement system includes a first electrochemical cell 202a, a second electrochemical cell 202b, and a third electrochemical cell 202c, each containing an electrolyte solution 201. The first electrochemical cell 202a contains a first reference electrode 203a and a first counter electrode 204a along with the electrolyte solution 201. The second electrochemical cell 202b contains a second reference electrode 203a and a second counter electrode 204a along with the electrolyte solution 201. The third electrochemical cell 202c contains a third reference electrode 203c and a third counter electrode 204c along with the electrolyte solution 201. The electrolyte solution 201 may be, for example, a 0.1 M NaOH aqueous solution. Each reference electrode may be, for example, an Ag / AgCl (silver-silver chloride) electrode. Each counter electrode may be a Pt electrode.

[0017] Further, a sample fixing portion 205 is provided in a part of the first electrochemical cell 202 a, the second electrochemical cell 202 b, and the third electrochemical cell 202 c to fix a test piece 100 (metal plate 101) to be measured, which serves as a working electrode. When the sample fixing portion 205 is viewed from above, the second electrochemical cell 202 b is arranged in a ring shape surrounding the periphery of the circular first electrochemical cell 202 a.

[0018] When the sample fixing portion 205 is viewed from above, a third electrochemical cell 202c having a circular ring shape is disposed surrounding the second electrochemical cell 202b. In the sample fixing portion 205 configured in this manner, the first electrochemical cell 202a, the second electrochemical cell 202b, and the third electrochemical cell 202c are each opened, and the electrolyte solution 201 comes into contact with (wets) the second surface 112 side (metal layer 102) of the specimen 100 fixed to the sample fixing portion 205 at each open portion.

[0019] 3 , a circular first region 151 in the center of the region surrounded by the support frame 105 on the second surface 112 side (metal layer 102) comes into contact with the electrolyte solution 201 at the open portion of the first electrochemical cell 202a of the sample fixing portion 205. A circular second region 152 surrounding the first region 151 on the second surface 112 side (metal layer 102) comes into contact with the electrolyte solution 201 at the open portion of the second electrochemical cell 202b of the sample fixing portion 205. A circular third region 153 surrounding the second region 152 on the second surface 112 side (metal layer 102) comes into contact with the electrolyte solution 201 at the open portion of the third electrochemical cell 202c of the sample fixing portion 205. The first region 151, the second region 152, the third region 153, and the through-hole 104 can be circular regions concentric with each other.

[0020] A first O-ring 215a and a second O-ring 215b are provided so that the electrolyte solution 201 in each of the first electrochemical cell 202a, the second electrochemical cell 202b, and the third electrochemical cell 202c can contact the metal layer 102 without coming into contact with each other (while being insulated and separated from each other). A third O-ring 215c is provided to prevent the electrolyte solution 201 from leaking from the outermost third electrochemical cell 202c in the sample fixing portion 205.

[0021] The first O-ring 215a is fixed to the outer periphery of the first electrochemical cell 202a in the sample fixing portion 205. The second O-ring 215b is fixed to the outer periphery of the second electrochemical cell 202b in the sample fixing portion 205. The third O-ring 215c is fixed to the outer periphery of the third electrochemical cell 202c in the sample fixing portion 205.

[0022] The measurement system also includes a measuring device 210 that controls the potential of the metal plate 101, which serves as the working electrode, to a constant value relative to the first reference electrode 203a and measures the current flowing between the working electrode and the first counter electrode 204a. The measuring device 210 controls the potential of the metal plate 101, which serves as the working electrode, to a constant value relative to the second reference electrode 203b and measures the current flowing between the working electrode and the second counter electrode 204b. The measuring device 210 also controls the potential of the metal plate 101, which serves as the working electrode, to a constant value relative to the second reference electrode 203c and measures the current flowing between the working electrode and the third counter electrode 204c. The measuring device 210 can be, for example, a potentiostat. By performing constant potential polarization measurements using the measuring device 210, the amount of hydrogen that has penetrated through the first surface 111 of the metal plate 101 can be measured.

[0023] Using the above-described measurement system, in each of the first region 151, the second region 152, and the third region 153, the metal plate 101 is used as the working electrode, and in each of the first region 151, the second region 152, and the third region 153, the amount of hydrogen that has penetrated through the first surface 111 of the metal plate 101 is measured by constant-potential polarization measurement using the first reference electrode 203a, the second reference electrode 203b, the third reference electrode 203c, and the counter electrodes 204a, the second counter electrode 204b, and the third counter electrode 204c in each of the electrolyte solutions 201 that have been individually brought into contact with the metal plate 101 (metal layer 102).

[0024] The corrosive environments of the first region 151, the second region 152, and the third region 153 of the metal plate 101 are different because they are all at different distances from the through hole 104 of the material piece 103. However, the corrosive environments on opposite sides of the same tank can be considered to be the same corrosive environment because they are all at the same distance from the hole. By measuring the amount of hydrogen penetration in each of the first region 151, the second region 152, and the third region 153, it is possible to evaluate the non-uniformity of the amount of hydrogen penetration that occurs in a crevice corrosion environment.

[0025] As explained above, according to the above-mentioned embodiment of the present invention, a material piece having a through hole formed in the center and spaced apart from the metal plate is arranged approximately parallel to the metal plate, and the material piece is supported on the metal plate by a support frame arranged in a ring-shaped position centered on the position of the through hole, and a container is formed by the metal plate, material piece, and support frame, so that it becomes possible to determine where and how much hydrogen has penetrated into the metal plate.

[0026] It should be noted that the present invention is not limited to the embodiments described above, and it is clear that many modifications and combinations can be made by a person having ordinary knowledge in the art within the technical concept of the present invention.

[0027] 100...test specimen, 101...metal plate, 102...metal layer, 103...material piece, 104...through hole, 105...support frame, 111...first surface, 112...second surface.

Claims

1. A specimen comprising: a metal plate; a metal layer made of Pd or Ni formed on a first surface of the metal plate; a material piece arranged approximately parallel to and spaced from the metal plate on a second surface of the metal plate opposite the first surface, the material piece having a through hole formed in the center; and an annular support frame supporting the material piece on the metal plate at a circular position centered on the position of the through hole, wherein the metal plate, the material piece, and the support frame form a container whose bottom is the second surface of the metal plate.

2. A specimen according to claim 1, wherein the support frame is an O-ring.

3. A method for measuring hydrogen penetration amount using a specimen comprising: a metal plate; a metal layer made of Pd or Ni formed on a first surface of the metal plate; a plate-shaped material piece arranged substantially parallel to and spaced from the metal plate on a second surface of the metal plate opposite the first surface, the plate having a through hole formed in its center; and an annular support frame supporting the material piece on the metal plate at an annular location centered on the position of the through hole, the metal plate, the material piece, and the support frame forming a container whose bottom is the second surface of the metal plate, wherein the method measures the amount of hydrogen that has penetrated from the first surface of the metal plate by constant-potential polarization measurement using a reference electrode and a counter electrode in each of an electrolyte solution that is individually brought into contact with the metal layer in each of a first circular region in the center of the region surrounded by the support frame, a second circular region surrounding the first region, and a third circular region surrounding the second region.

4. A method for measuring hydrogen penetration amount according to claim 3, wherein the support frame is an O-ring, and the electrolytic solution is brought into contact with the metal layers of the first region, the second region, and the third region while being insulated and separated from each other by the O-ring.

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