Method for evaluating hydrogen generation reactions

Abstract

In Step S101, a steel material to be evaluated is charged with hydrogen until the hydrogen storage capacity thereof is saturated (Step S102) (first process). Next, in Step S103, the steel material with saturated hydrogen storage capacity, which is used as a working electrode, a reference electrode, and a counter electrode are immersed in an electrolyte solution containing an additive that promotes penetration of hydrogen into the steel material, and a change in electric current flowing between the steel material and the counter electrode is measured when the voltage between the steel material and the reference electrode is swept (second process). Next, in Step S104, a hydrogen evolution reaction on the surface of the steel material is evaluated on the basis of the measured change in the electric current (third process).

Description

Technical Field

[0001] The present invention relates to a method for evaluating a hydrogen generation reaction.

Background Art

[0002] When high-strength steel contains hydrogen, its ductility is lost and its strength is significantly reduced. This phenomenon is called hydrogen embrittlement. Regarding such hydrogen embrittlement of steel, a hydrogen embrittlement acceleration test has been carried out for the purpose of evaluating the hydrogen embrittlement resistance characteristics of steel and predicting the occurrence of hydrogen embrittlement.

[0003] In the hydrogen embrittlement acceleration test, in order to allow hydrogen to penetrate into the steel (absorb hydrogen into the steel), the cathodic charging method in an aqueous solution added with an additive that promotes hydrogen penetration, such as ammonium thiocyanate, is widely used. In the cathodic charging method, the amount of hydrogen absorbed by the steel is determined by the hydrogen generation reaction on the steel surface. Since the evaluation may be performed by changing the test conditions in the hydrogen embrittlement acceleration test, it is important to evaluate the hydrogen generation reaction under a certain test condition, that is, to obtain the reaction rate coefficients of the Volmer reaction, Heyrovsky reaction, and Tafel reaction, which are hydrogen generation reactions, in order to accurately grasp the behavior of hydrogen penetration into the steel in the acceleration test.

[0004] As a method for evaluating the hydrogen generation reaction on the steel surface, there is a method using a hydrogen permeation test (see Non-Patent Document 1). In addition, there is a method for evaluating the hydrogen generation reaction on the steel surface by numerical calculation from the polarization curve (see Non-Patent Document 2).

Prior Art Documents

Non-Patent Documents

[0005]

Non-Patent Document 1

[0006] The method of evaluating hydrogen evolution reactions on steel surfaces using hydrogen permeation tests is limited to thin, plate-shaped steel materials. Therefore, this evaluation method cannot be applied to rod-shaped steel materials, etc. Furthermore, the method described in Non-Patent Literature 2 is limited to cases where hydrogen penetration into the steel is very small, such as cathode charging in an aqueous solution without additives that promote hydrogen penetration. In evaluating (measuring) hydrogen evolution reactions on steel surfaces in the environment of accelerated hydrogen embrittlement testing, the test is conducted in an aqueous solution with additives that promote hydrogen penetration. In this measurement environment, the steel material is in a state where it is trying to absorb a large amount of hydrogen, so it is not possible to accurately measure (evaluate) the hydrogen evolution reaction on the steel surface. Thus, conventional techniques have the problem that they cannot accurately evaluate hydrogen evolution reactions on steel surfaces in the environment of accelerated hydrogen embrittlement testing, especially for rod-shaped steel materials, etc.

[0007] This invention was made to solve the above-mentioned problems and aims to accurately evaluate the hydrogen generation reaction on the surface of steel materials, such as rod-shaped steel materials, in the environment of an accelerated hydrogen embrittlement test. [Means for solving the problem]

[0008] The hydrogen generation reaction evaluation method according to the present invention comprises: a first step of charging a steel material to be evaluated with hydrogen until its hydrogen storage capacity is saturated; a second step of immersing a steel material with saturated hydrogen storage capacity, a reference electrode, and a counter electrode in an electrolyte solution to which an additive that promotes the penetration of hydrogen into the steel material is added, and measuring the change in current flowing between the steel material and the counter electrode when the voltage between the steel material and the reference electrode is swept; and a third step of evaluating the hydrogen generation reaction on the surface of the steel material based on the measured change in current. [Effects of the Invention]

[0009] As explained above, according to the present invention, since hydrogen is charged into the steel material under evaluation until the hydrogen storage capacity is saturated, and then hydrogen generation in the steel material is measured, the hydrogen generation reaction on the surface of the steel material in the environment of an accelerated hydrogen embrittlement test, targeting rod-shaped steel materials and the like, can be accurately evaluated. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a flowchart illustrating a hydrogen generation reaction evaluation method according to an embodiment of the present invention. [Figure 2] Figure 2 is a diagram showing the configuration of a measurement system for implementing the hydrogen generation reaction evaluation method according to an embodiment of the present invention. [Figure 3] Figure 3 is a characteristic diagram showing the polarization curve obtained from actual measurements. [Figure 4] Figure 4 is a configuration diagram showing an example of the configuration of an apparatus for performing hydrogen charging in the hydrogen generation reaction evaluation method according to an embodiment of the present invention. [Modes for carrying out the invention]

[0011] The hydrogen generation reaction evaluation method according to an embodiment of the present invention will be described below with reference to Figure 1.

[0012] First, in step S101, hydrogen is charged into the steel material to be evaluated until the hydrogen storage capacity is saturated (step S102) (first step). For example, hydrogen can be charged into the steel material by a cathode hydrogen charging method using an electrolyte solution to which an additive that promotes the intrusion (storage) of hydrogen into the steel material is added.

[0013] Next, in step S103, the steel material that will serve as the working electrode, which is saturated with hydrogen, the reference electrode, and the counter electrode are immersed in an electrolyte solution to which an additive that promotes the penetration of hydrogen into the steel material is added, and the change in the current flowing between the steel material and the counter electrode is measured when the voltage between the steel material and the reference electrode is swept (second step).

[0014] Next, in step S104, the hydrogen evolution reaction on the surface of the steel material is evaluated based on the measured change in current (third step). For example, the reaction rate coefficient of the hydrogen evolution reaction can be determined based on the measured change in current, and the hydrogen evolution reaction on the surface of the steel material can be evaluated from the determined reaction rate coefficient.

[0015] The measurement system for performing the hydrogen generation reaction evaluation method can include a container 101 made of acrylic resin or the like, and an electrolyte solution 102 contained in the container 101, as shown in Figure 2. The electrolyte solution 102 is, for example, a 1 mol / L aqueous solution of sodium bicarbonate, to which an additive that promotes hydrogen entry is added. The additive can be ammonium thiocyanate. For example, 0.1 mol / L of ammonium thiocyanate can be added to a 1 mol / L aqueous solution of sodium bicarbonate (electrolyte solution 102). Note that the additive is not limited to ammonium thiocyanate; for example, sodium sulfide (Na2S), phosphorus or calcium (Ca3P2), etc., can be used.

[0016] In addition, this measurement system includes a reference electrode 103 and a counter electrode 104 immersed in an electrolyte solution 102. The reference electrode 103 is, for example, an Ag / AgCl (silver-silver chloride) electrode, and the counter electrode 104 is a Pt electrode. Also, a steel material 151 serving as a working electrode is immersed in the electrolyte solution 102. For example, the steel material 151 is in the shape of a bar with a circular cross-section having a diameter of 7.2 mm and a length of 30 mm. The reference electrode 103, the counter electrode 104, and the steel material 151 are connected to an electrochemical measurement device 105 via wiring. The electrochemical measurement device 105 is, for example, a potentiostat.

[0017] By using this measurement system, hydrogen charging can be carried out. A three-electrode configuration is adopted with the steel material 151 as the working electrode, the reference electrode 103 and the counter electrode 104. The liquid temperature of the electrolyte solution 102 is 30°C, and the cathodic charging current density with respect to the steel material 151 is 10 A / m ,

[0019] ,

[0018] , , , It can be set as such. Note that these conditions are the electrochemical conditions under which the surface of the steel material 151 in contact with the electrolyte solution 102 does not corrode. By performing cathodic charging in this way, hydrogen is generated on the surface of the steel material 151. As a result, the steel material 151 is in a state where hydrogen is occluded (absorbed). In this way, by the cathodic hydrogen charging method, hydrogen is generated on the surface of the steel material 151 and the steel material 151 is made to occlude (absorb) hydrogen. By performing cathodic charging for 72 hours under the above-described conditions, the amount of hydrogen occlusion in the steel material 151 can be made to reach a saturated state.

[0018] As described above, once the amount of hydrogen occlusion in the steel material has reached a saturated state (first step), promptly, the measurement of the change in current (polarization curve measurement) in the second step is carried out. The range for sweeping the voltage applied between the steel material and the reference electrode is from the natural potential to -1.2 V vs. Ag / AgCl, and the voltage scanning speed is 20 mV / min. By this polarization curve measurement, the polarization curve shown in FIG. 3 is obtained.

[0019] For the obtained polarization curve, the hydrogen evolution reaction is evaluated using a well-known numerical calculation method (Non-Patent Document 2). Assuming that the reaction rate coefficients of the Volmer reaction, Heyrovsky reaction, and Tafel reaction, which are hydrogen evolution reactions, are k1, k2, and k3, respectively, the cathode charge current density ic can be expressed by the following equation using k1, k2, and k3. In the equation, F is the Faraday constant.

[0020]

Number

[0021] Also, k1 and k2 in the above equation can be expressed by the following equation using the potential E. Here, k1 when k1’E = 0, k2’ is k2 when E = 0, α is the charge transfer coefficient (= 0.5), R is the gas constant, and T is the absolute temperature.

[0022]

Number

[0023] By fitting the equation of the cathode charge current density ic expressed using k1, k2, and k3 and the above polarization curve using the least squares method, the values of k1, k2, and k3 can be obtained. The fitting range can be set to ±100 mV centered on the potential at the time of the cathode charge current density of 10 A / m 2 .

[0024] The fitting result is shown by the solid line in FIG. 3. The values of k1, k2, and k3 at the time of the cathode charge current density of 10 A / m 2 are calculated to be 1.7×10 -4 , 1.3×10 -8 , and 3.2×10 -4 , respectively, and the hydrogen evolution reaction on the steel surface during the hydrogen embrittlement acceleration test could be evaluated.

[0025] In the above description, hydrogen is absorbed into the steel material electrochemically (cathode charge) using an additive that promotes hydrogen intrusion, such as ammonium thiocyanate, in the first step, but this is not the only method. In the first step, hydrogen can be charged into the steel material by placing it in a hydrogen atmosphere. For example, as shown in Figure 4, hydrogen supplied from a hydrogen gas cylinder 201 is pumped by a pump 202 to create a high-pressure hydrogen environment (a hydrogen atmosphere at a pressure higher than atmospheric pressure) in a pressure chamber 203. By placing the round steel bar 204 to be measured inside this chamber for a certain period of time, hydrogen can be absorbed into the steel material and a hydrogen-saturated state can be created.

[0026] As described above, according to the present invention, since hydrogen is charged into the steel material under evaluation until the hydrogen storage capacity is saturated, and then hydrogen generation in the steel material is measured, it becomes possible to accurately evaluate the hydrogen generation reaction on the surface of the steel material in the environment of an accelerated hydrogen embrittlement test, targeting rod-shaped steel materials and the like.

[0027] Some or all of the above embodiments may also be described as follows, but are not limited to the following:

[0028] [Note 1] The first step involves charging the steel material under evaluation with hydrogen until its hydrogen storage capacity is saturated, The second step involves immersing a steel material saturated with hydrogen (which serves as the working electrode), a reference electrode, and a counter electrode in an electrolyte solution containing an additive that promotes hydrogen penetration into the steel material, and measuring the change in current flowing between the steel material and the counter electrode when the voltage between the steel material and the reference electrode is swept. A third step involves evaluating the hydrogen evolution reaction on the surface of the steel material based on the measured change in current. A method for evaluating hydrogen generation reactions, comprising the following components.

[0029] [Note 2] In the hydrogen generation reaction evaluation method described in Appendix 1, A method for evaluating hydrogen generation reactions, characterized in that the additive is ammonium thiocyanate.

[0030] [Note 3] In the hydrogen generation reaction evaluation method described in Appendix 1 or 2, The first step is a hydrogen generation reaction evaluation method characterized by charging hydrogen into a steel material using a cathode hydrogen charging method with an electrolyte solution.

[0031] [Note 4] In the hydrogen generation reaction evaluation method described in Appendix 1 or 2, The first step is a hydrogen generation reaction evaluation method characterized by charging steel materials with hydrogen by placing them in a hydrogen atmosphere.

[0032] [Note 5] In the hydrogen generation reaction evaluation method described in Appendix 4, The first step is a hydrogen generation reaction evaluation method characterized by charging the steel material with hydrogen by placing it in a hydrogen atmosphere at a pressure higher than atmospheric pressure.

[0033] [Note 6] In the hydrogen generation reaction evaluation method described in any one of the appendices 1 to 5, The third step is a hydrogen evolution reaction evaluation method that determines the reaction rate coefficient of the hydrogen evolution reaction based on the measured change in current, and evaluates the hydrogen evolution reaction on the surface of the steel material based on the determined reaction rate coefficient.

[0034] 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 implemented within the technical concept of the present invention by those with ordinary skill in the art. [Explanation of symbols]

[0035] 101...Container, 102...Electrolyte solution, 103...Reference electrode, 104...Counter electrode, 105...Electrochemical measuring device, 151...Steel material.

Claims

1. The first step involves charging the steel material under evaluation with hydrogen until its hydrogen storage capacity is saturated, A second step involves immersing the steel material, which has a saturated hydrogen storage capacity serving as the working electrode, a reference electrode, and a counter electrode in an electrolyte solution containing an additive that promotes hydrogen penetration into the steel material, and measuring the change in current flowing between the steel material and the counter electrode when the voltage between the steel material and the reference electrode is swept. A third step involves evaluating the hydrogen generation reaction on the surface of the steel material based on the measured change in current. A method for evaluating hydrogen generation reactions, comprising the following components.

2. In the hydrogen generation reaction evaluation method according to claim 1, A method for evaluating a hydrogen generation reaction, characterized in that the additive is ammonium thiocyanate.

3. In the hydrogen generation reaction evaluation method according to claim 1, The first step is a method for evaluating a hydrogen generation reaction, characterized in that hydrogen is charged to the steel material by a cathode hydrogen charging method using the electrolyte solution.

4. In the hydrogen generation reaction evaluation method according to claim 1, The first step is a method for evaluating a hydrogen generation reaction, characterized in that hydrogen is charged to the steel material by placing the steel material in a hydrogen atmosphere.

5. In the hydrogen generation reaction evaluation method according to claim 4, The first step is a method for evaluating a hydrogen generation reaction, characterized in that hydrogen is charged to the steel material by placing the steel material in a hydrogen atmosphere at a pressure higher than atmospheric pressure.

6. In the hydrogen generation reaction evaluation method according to any one of claims 1 to 5, The third step is a hydrogen evolution reaction evaluation method characterized by determining the reaction rate coefficient of the hydrogen evolution reaction based on the measured change in current, and evaluating the hydrogen evolution reaction on the surface of the steel material based on the determined reaction rate coefficient.

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