JP5979731B2 - Method for monitoring the amount of hydrogen entering the metal part of a moving object - Google Patents

Description

The present invention relates to a method for measuring the amount of hydrogen penetrating into a metal, which can accurately detect the amount of hydrogen penetrating into the metal due to corrosion.
Further, the present invention uses the above measurement method to corrode each part of a metal material constituting a moving body such as an automobile, a ship, and a railway vehicle in a corrosive environment exposed in a use state. The present invention relates to a monitoring method capable of continuously detecting the amount of hydrogen generated and entering into a metal material.

In recent years, from the viewpoint of preventing global warming, there has been a demand for weight reduction of vehicle bodies aimed at reducing CO ₂ emitted during driving of automobiles. Accordingly, efforts are being made to reduce the plate thickness by increasing the strength of the steel plate used.

With the increase in strength of the steel sheet described above, concerns about delayed fracture that has not been a problem with conventional automotive parts have emerged.
Delayed fracture is a phenomenon in which high-strength steel parts suddenly break brittlely with little plastic deformation in appearance when a certain amount of time has passed under the condition of static load stress. In a broad sense, liquid metal contact cracking and stress corrosion cracking are also included (Non-Patent Document 1), but the problem in automobiles is hydrogen embrittlement-type delayed fracture caused by hydrogen entering the steel due to corrosion. It is.

  Conventionally, it is widely known that bolts made of high-strength steel with a tensile strength of 1200 MPa or more cause delayed fracture in the atmospheric environment (Non-Patent Document 1). It is thought to be caused by hydrogen. From this viewpoint, various methods for evaluating delayed fracture focusing on hydrogen intrusion into steel have been proposed.

  For example, Patent Document 1 discloses an electrolytic cell for holding an electrolytic solution, a cathode for performing hydrogen charging on a U-shaped test piece to which a load stress is applied by U-bending a thin steel plate, and a U-bending of the test piece. An apparatus for evaluating hydrogen embrittlement of a thin steel sheet has been proposed, characterized in that it has an anode arranged so that the hydrogen concentration distribution in the part is within 50% of the average hydrogen concentration and a current generating means.

  Further, Patent Document 2 discloses that in a method for evaluating delayed fracture characteristics in which a steel material contains diffusible hydrogen by cathodic charging and the amount of critical diffusible hydrogen is measured to evaluate the delayed fracture property of the steel material, the critical diffusivity is determined. In order to prevent hydrogen from being released from the steel during measurement of the amount of hydrogen, a method of galvanizing the steel has been proposed.

  Furthermore, Non-Patent Document 2 reports an example in which a high-strength bolt that has been corroded for a certain period in an atmospheric exposure environment is collected and the hydrogen concentration occluded in the bolt is measured. Further, in this Non-Patent Document 2, from the change of the anode current value detected from the opposite surface side by the electrochemical hydrogen permeation method using a test apparatus that exposes one side of a steel sheet to the external environment, The results of investigating the hydrogen intrusion behavior due to corrosion in the sea are reported.

  As described above, the metal material that is most concerned about the problem of delayed fracture is a steel material that is widely used as a practical material. However, the problem of delayed fracture will also occur in other metal materials in the future. The possibility is pointed out (for example, non-patent document 3).

JP 2005-134152 A JP 2005-69815 A

"Matsuyama Junsaku: Delayed Destruction, Nikkan Kogyo Shimbun, Tokyo, (1989)" “Omura et al .: Iron and Steel, Vol.91, No.5, p.42 (2005)” “Takatori et al .: Iron and Steel, Vol.78, No.5, p.149 (1992)” "M.A.V. Devanathan, Z.Stachurski; Proc. Roy. Soc. London, Ser. A, 270, 90 (1962)"

  The technique described in Patent Document 1 is an accelerated test in which hydrogen is forcibly entered from the outside by electrolysis using a U-bent portion of a thin steel plate as a cathode, and therefore under conditions different from the actual usage environment. Although it is possible to give superiority or inferiority to the occurrence of delayed fracture depending on the type of test material, it is not a judgment material for estimating whether or not delayed fracture occurs depending on the amount of hydrogen intrusion due to corrosion in the actual use environment.

  Similarly, in Patent Document 2, since the hydrogen intrusion into the steel is due to cathodic charging, it is not possible to determine whether or not delayed fracture occurs depending on the amount of hydrogen intrusion due to corrosion in the actual use environment. Can not.

Furthermore, the data obtained by the atmospheric exposure test disclosed in Non-Patent Document 2 are only test results under environmental factors associated with the terrain specific environment, and various data that change with the movement of the structure. No consideration has been given to continuously assessing corrosion in the environment.
Further, in the hydrogen permeation test in the atmospheric exposure using the test apparatus that exposes one side of the steel sheet to the external environment shown in Non-Patent Document 2, the change in the residual current on the anode side accompanying the temperature change in the environment is not taken into consideration. For this reason, there was a problem in the quantitativeness of the measured value.

As described above, in a moving body such as an automobile, when the terrain environment is changed by moving, and physical factors (for example, vibration, dust accumulation-dropping, water / mud splash adhesion-drying, etc.) are added. The corrosive environment may change drastically.
However, there have been no examples of continuously and quantitatively measuring the amount of hydrogen intrusion due to corrosion of a moving body in which physical factors such as vibrations and terrain environmental changes cannot be avoided.

The present invention has been developed in view of the above situation, and accurately measures the amount of hydrogen penetrating into the metal due to corrosion in consideration of the change in the residual current on the anode side accompanying the temperature change in the environment. The purpose is to propose a method for measuring the amount of hydrogen penetrating into a metal.
Further, the present invention uses the above-described measurement method to cause each part of the metal material that constitutes the moving body whose environment changes rapidly, accompanied by corrosion in a corrosive environment exposed in use, An object of the present invention is to propose a method for monitoring the amount of hydrogen entering a metal part of a moving body, which can continuously monitor the amount of hydrogen entering the material.

As a result of intensive studies to achieve the above object, the present inventors have developed a new method for measuring the amount of invading hydrogen based on the electrochemical principle.
And when this measuring method was utilized, it also discovered that the hydrogen which penetrate | invades with corrosion of the metal component which comprises a moving body can be monitored continuously.
The present invention is based on the above findings.

That is, the gist configuration of the present invention is as follows.
1. A method for monitoring the amount of hydrogen entering a metal part of a moving body,
A method for measuring the amount of hydrogen penetrating into the interior of a metal is applied to a metal part to be evaluated of a moving body, at least a part of which is made of a metal material, and the amount of hydrogen penetrating into the metal due to corrosion of the metal part to be evaluated Is continuously measured in a corrosive environment that varies with the traveling environment of the moving body,
A method for measuring the amount of hydrogen penetrating into the metal is
This is a method of measuring the amount of hydrogen generated by corrosion of metal materials and penetrating into the interior of the metal using a multi-channel potentiostat using the electrochemical hydrogen permeation method , and corrodes one side of the metal material as the specimen. In the state where the intrusion surface of hydrogen that is exposed to the environment and generated by a corrosion reaction is used, the other surface of the subject is a hydrogen detection surface, and the potential on the hydrogen detection surface side is maintained at −0.1 to +0.3 V vs. SCE. When measuring the flux of hydrogen diffusing to the detection surface as an anode current,
An electrochemical cell composed of a plurality of cell groups divided into at least two cells is disposed on the hydrogen detection surface side of the same subject, and each cell in the cell group has a pH of 9 to 13 Fill with electrolyte solution and install independent reference electrode and counter electrode,
At least one cell in the cell group is used as a reference cell for correcting the residual current, and a protective film that blocks contact with the corrosive environment is provided at a location corresponding to the hydrogen entry surface side of the reference cell,
Of the hydrogen intrusion surface of the specimen, in a location corresponding to a cell other than the reference cell, the metal material is directly exposed to a corrosive environment without providing a protective film,
An anode current value detected in a cell other than the reference cell is corrected by a residual current value detected in the reference cell, and an intrusion hydrogen amount from the corroded surface side is calculated based on the corrected anode current value. And a method for monitoring the amount of hydrogen entering the metal part of the moving body .
However, the intrusion hydrogen amount (permeated hydrogen amount) is converted according to the following equation.
The value obtained by subtracting the anode current density value detected in the reference cell from the anode current density value detected in a cell other than the reference cell is a permeated hydrogen current density: i _H (μA / cm ² = 10 ⁻⁶ A / cm ² ), The amount of invading hydrogen per unit area: M _H (mol / scm ² ) or m _H (pieces / scm ² )
M _H = i _H × 1.036 × 10 ^-11 (mol / scm ² ),
m _H = i _H x 6.24 x 10 ¹² (pieces / scm ² )
Ask for.

2. 2. The method for monitoring the amount of hydrogen penetrating into the metal part of the moving body according to 1 above, wherein an Ir / Ir oxide electrode is used as the reference electrode.

3. 3. Monitoring the amount of hydrogen penetrating into the metal part of the moving body according to 1 or 2 above, wherein the surface on the hydrogen detection surface side of the subject is coated with Pd or a Pd-containing alloy or Ni in advance. Way .

4 . The metal part of the mobile body according to any one of claims 1 to 3 , wherein the delayed fracture sensitivity of the metal part is evaluated from the amount of hydrogen that penetrates into the metal part to be evaluated of the mobile body. How to monitor the amount of hydrogen entering the interior.

According to the present invention, it is possible to accurately detect the amount of hydrogen that penetrates into the metal due to corrosion.
Further, according to the present invention, each part of a metal material constituting a moving body such as an automobile, a ship, and a railway vehicle is generated as it corrodes in a corrosive environment exposed in its use state. It is possible to continuously monitor the amount of hydrogen penetrating into the gas and obtain the information necessary to determine whether delayed destruction occurs due to the amount of hydrogen penetrating due to corrosion in the actual usage environment. .

It is explanatory drawing of an electrochemical hydrogen permeation method. It is the figure which showed typically the suitable cell structure used for implementation of this invention. It is the figure which showed typically reaction by the corrosion surface (hydrogen intrusion surface) side and hydrogen detection surface side of a cell without a protective film. FIG. 6 is a graph showing a change in potential with time when an Ir line is immersed in a 0.2 M NaOH aqueous solution. It is the figure which showed the change of the temperature and humidity in an Example. It is the figure which showed the time-dependent change of the anode current detected by each channel. It is an external appearance photograph of the corrosion side of the sample after the experiment. It is the figure which showed typically the measurement system at the time of mounting a measuring apparatus in a motor vehicle and measuring an anode current. The figure which compared and showed the difference of the anode current density measured in each site | part of a motor vehicle with the case where correction | amendment by the reference electrode according to this invention was performed (invention example), and the case where correction | amendment was not performed (comparative example). is there.

  The present invention is a technique that can be applied to various vehicles such as automobiles, motorcycles, railways, and mobile bodies that can be moved on their own, such as ships, aircraft, etc. explain. The metal material to be evaluated is not necessarily limited to a steel plate, but here, a case where it is applied to a steel plate will be described as a representative example.

  The present invention measures the amount of hydrogen generated by metal material corrosion and penetrating into the interior by applying the measurement principle of the electrochemical hydrogen permeation method. By exposing, the hydrogen generated during the corrosion penetrates into the steel, and the amount of penetrating hydrogen is measured by taking out hydrogen from the opposite side.

The electrochemical hydrogen permeation method is a technique developed by Devanathan and Stachurski in 1962 (Non-Patent Document 4). As schematically shown in FIG. 1, two electrolytic cells 1a and 1b are formed of one sample 2 It is arranged facing each other across. In the case of the figure, the sample surface of the left electrolytic cell 1a is cathode-polarized at a constant potential or a constant current to generate hydrogen and charge, and the right electrolytic cell 1b is subjected to constant-potential anodic polarization. The hydrogen permeated through 2 is oxidized into hydrogen ions, and the amount of permeated hydrogen is determined from the current value.
In the figure, reference numerals 3a and 3b are reference electrodes, 4a and 4b are electrodes, and 4b is particularly referred to as a counter electrode or a coefficient electrode. The electrode 4a is connected to a potentiostat for applying a constant potential or a galvanostat for applying a constant current, and one of the electrodes 4b is connected to a potentiostat for applying a constant potential. Reference numerals 5a and 5b denote sintered glass frits for removing the influence of gas and the like generated at the counter electrodes 4a and 4b.

The above-described electrochemical hydrogen permeation method itself is a method that has been well known as “a method for measuring a hydrogen diffusion coefficient in a steel sheet”.
As shown in FIG. 1, the original electrochemical hydrogen permeation method is a method in which hydrogen is electrolytically charged with one side of the sample as a cathode and extracted with the opposite side as an anode. A study has been reported in which the surface corresponding to the hydrogen charge surface is exposed to a corrosive environment (Non-Patent Document 2).
However, as described above, the measurement method disclosed in Non-Patent Document 2 has a problem that the change in the measurement current value due to the change in temperature is not taken into consideration. In addition to the hydrogen oxidation current, the anode holding current measured on the hydrogen detection surface side by the electrochemical hydrogen permeation method is superimposed with the passive holding current of the test material. This passive holding current is the main component of the residual current, and is influenced by various factors, but it varies greatly with temperature.

  Since the anode current measured on the hydrogen detection surface side by the electrochemical hydrogen permeation method is weak, accurate anode current cannot be measured unless the temperature dependence of the residual current is corrected.

  In order to solve the above problem, the present inventors have made various studies, and as a result, the electrochemical cell provided on the hydrogen detection surface side is divided into at least two or more divided on the same subject. It is composed of a group of cells, and at least one of the cells is used as a reference cell for correcting the residual current, and a protective film for blocking the corrosive environment is provided at a portion corresponding to the hydrogen entry surface side of the reference cell. By providing it, the temperature dependence of the residual current can be corrected.

FIG. 2 schematically shows the cell structure of the present invention. In the example of FIG. 2, four cells 7a, 7b, 7c, 7d are provided on the hydrogen detection surface side of a steel plate 6 as an object, and the leftmost cell 7a is a reference cell for correcting the residual current. It is. In the figure, reference numeral 8 is a counter electrode (Pt line), and 9 is a reference electrode (Ir line).
In the figure, the surface temperature of the steel plate in each cell, the temperature of the electrolyte solution in the cell, etc. are all the same temperature. A protective film 10 is provided on the hydrogen entry surface side of the reference cell 7a. Since the portion covered with such a protective film 10 does not corrode and therefore does not enter hydrogen, the current measured on the hydrogen detection surface side of the reference cell is considered as the residual current itself.

FIG. 3 schematically shows reactions on the corroded surface (hydrogen intrusion surface) side and the hydrogen detection surface side of a cell (also referred to as a channel) without a protective film.
By maintaining the surface potential on the hydrogen detection surface side at a potential sufficient for the ionization reaction of hydrogen, all the hydrogen that has reached the detection surface side by diffusion is taken out as hydrogen ions. In the present invention, the surface of the steel plate on the hydrogen detection surface side is passivated. Thereby, it can be considered that the anode current detected on the hydrogen detection side substantially corresponds to the hydrogen permeation current.
Therefore, by correcting the current value thus obtained with the residual current value obtained by the reference cell, an accurate anode current value can be measured regardless of the change in the residual current due to the temperature change. Thus, it is possible to calculate an accurate intrusion hydrogen amount based on the anode current value.

Hereinafter, the present invention will be specifically described.
In the present invention, in order to keep the steel plate on the hydrogen detection surface side in a passive state, the solution in the anode electrode chamber needs to be an electrolyte solution having a pH of 9 to 13. This is because if the pH is less than 9, it is difficult to maintain the surface passivation of the steel sheet at a given potential, while if the pH exceeds 13, damage to the environment will occur if it is accidentally leaked. Because is big. As an electrolyte solution having an appropriate pH, an aqueous NaOH solution of about 0.1 to 0.5 M (mol / liter) is suitable. In the present invention, the electrolyte solution having an appropriate pH is not necessarily limited to a 0.1 to 0.2 M NaOH aqueous solution, but when the steel plate surface of the hydrogen detection surface is maintained at a potential sufficient for the ionization reaction of hydrogen. Any electrolyte solution can be used as long as it can ensure a passivated state of the surface of the steel sheet. Furthermore, using a gel electrolyte instead of the electrolyte solution is advantageous not only for preventing liquid leakage but also for ease of handling.

In the present invention, the potential of the hydrogen detection surface must be kept at −0.1 to +0.3 V vs. SCE at all times. This is because if the potential of the hydrogen detection surface is out of this range, a stable hydrogen ionization current cannot be obtained.
Here, SCE is a saturated calomel electrode, and the potential of this SCE with respect to the standard hydrogen electrode (SHE) is represented by +0.244 V (vs SHE, 25 ° C.).

In addition, as the reference electrode for controlling the potential, various electrodes that are currently in practical use can be used.
However, when using an electrode containing chloride such as an Ag / AgCl electrode, contamination of the chloride ion into the anode electrode chamber solution destroys the passivation of the sample surface, increasing the residual current, resulting in a measured value. May be inaccurate.

Therefore, as a result of various studies on reference electrodes that can avoid the above-mentioned problems, it has been clarified that an Ir / Ir oxide electrode can be obtained by immersing Ir wire in an anode electrode chamber solution, and a stable potential can be obtained for a long time. It was done. That is, the most suitable electrode as the reference electrode is an Ir / Ir oxide electrode.
FIG. 4 shows the results of examining the time-dependent change in potential when the Ir line is immersed in a 0.2 M NaOH aqueous solution. The potential change at the initial stage of immersion is considered to be the time until Ir oxide (IrO) is stably formed on the surface of the Ir wire. However, it can be seen that a potential of about −0.04 vs. SSE is stably obtained after a predetermined time has elapsed.
Here, SSE is a silver-silver chloride electrode, and the potential of this SSE with respect to a standard hydrogen electrode (SHE) is represented by +0.199 V (vs SHE, 25 ° C.).

  In the present invention, the surface of the hydrogen detection surface is preferably coated with a metal having a large hydrogen diffusion constant and promoting the oxidation reaction of hydrogen. Examples of such a metal include Pd, Pd alloy, Ni Etc. By coating these metals or alloys, it is possible not only to keep the residual current of the hydrogen detection surface at a low value, but also to promote the oxidation reaction of the intruding hydrogen on the hydrogen detection surface side. The sensitivity of the anode current due to ionization of can be increased. Note that Pd has an advantage that the hydrogen diffusion constant is larger than Ni and the temperature dependence of the residual current can be reduced.

When coating with Pd or a Pd alloy, plating may be performed by cathodic electrolysis in an aqueous solution containing palladium ions such as [Pd (NH ₃ ) ₄ ] Cl ₂ .H ₂ O. As the Pd alloy, Pd—Ni, Pd—Co alloy or the like can be used. Here, the film thickness of Pd plating or Pd alloy plating is preferably 10 to 100 nm.
In the case of coating with Ni, Ni plating may be performed by cathodic electrolysis in a known plating bath such as a watt bath. The thickness of the Ni plating is preferably 10 to 100 nm.
Further, Pd or a Pd alloy can be plated on the Ni plating.

  The protective film provided on the hydrogen entry surface is not particularly limited, and any protective film can be used as long as it can block the corrosive environment. Specific means includes attaching stainless steel foil.

As described above, according to the present invention, it is possible to accurately detect the amount of hydrogen that enters the interior of the metal due to corrosion regardless of environmental changes such as temperature changes.
Therefore, when the measurement method of the present invention is applied to a moving body such as an automobile, a ship, and a railway vehicle, each part of the metal material constituting the moving body is affected by a change in the environment exposed in the usage state. Therefore, the amount of hydrogen entering the metal material can be continuously and accurately monitored.
As a result, it is possible to accurately determine whether or not various types of moving bodies are delayed and destroyed by the amount of hydrogen intrusion due to corrosion in their actual use environment.

Example 1
The experiment was performed using a measuring device having four cells (CH1 to CH4) having the structure shown in FIG. As a test object, a mild steel plate having a thickness of 1.0 mm plated with Pd at a thickness of 100 nm on the hydrogen detection surface side was used. The reference cell was channel 3 (CH3), and a stainless steel foil was attached as a protective film to the portion corresponding to the corroded surface side of CH3. Drop 300 mL of 0.5M NaCl on the corrosive surface of each cell, then dry at 25 ° C and 35% RH (relative humidity) for 4 hours or more, then hold at 25 ° C and 85% RH (relative humidity) for 24 hours or more Then, the temperature was raised stepwise. The potential of the hydrogen detection surface was kept at 0 V vs SCE. The temperature change and humidity change at this time are shown in FIG.

Corresponding to the temperature change shown in FIG. 5, the change in the anode current density detected in each channel is shown in FIG.
It can be seen that the anode current density value of the reference electrode (CH3), which does not inherently corrode on the steel plate surface, also increases as the temperature increases. This is presumably because the residual current due to the oxidation current of Pd on the hydrogen detection surface side increased due to the temperature rise. Thus, the temperature dependence of the residual current is a level that cannot be ignored.

A photograph of the appearance of the corroded surface of the sample after the experiment is shown in FIG.
The reason why the anode current density value of 4Ch was smaller than that of other Ch is that the corrosion area on the hydrogen intrusion surface side corresponding to the detection surface was small because the position of 0.2M NaCl dropped first was shifted. .

Therefore, by subtracting the anode current density value of the reference electrode (CH3) from the anode current density values obtained for CH1 and CH2, it is possible to obtain an accurate permeated hydrogen current density value in each cell (CH1, CH2). Further, by averaging these values, the permeated hydrogen current density value of the specimen steel plate can be obtained.
Then, the permeated hydrogen amount (intrusion hydrogen amount) is calculated from the permeated hydrogen current density value obtained as described above by the following equation.
Thus, it is possible to detect an accurate permeated hydrogen current value and thus a permeated hydrogen amount (intruded hydrogen amount) regardless of the temperature change.

The permeated hydrogen amount is converted according to the following formula.
Permeated hydrogen current density i _H ( μ A / cm ² = 10 ⁻⁶ A / cm ² )
Permeated hydrogen per unit area _MH (mol / scm ² ), m _H (pieces / scm ² )
M _H = i _H × 1.036 × 10 ^-11 (mol / scm ² ),
m _H = i _H x 6.24 x 10 ¹² (pieces / scm ² )

Example 2
The measurement apparatus used in Example 1 was actually mounted on an automobile, and a measurement system schematically shown in FIG. 8 was constructed. Four channel cells were installed at three locations: a) a fender, b) a room, and c) under the floor (floor lower surface). A battery-powered multichannel potentiostat was created and housed in the trunk along with a dedicated battery. The test material is the same steel plate thickness of 1.0 mm as in Example 1, and the average speed of 40 km in the premises of the steel works for 6 hours from 9:00 to 15:00 every day for 5 days from Monday to Friday. Drive at / h. In addition, it will stop at the parking lot from 15:00 to 9:00 the next day.

The maximum value of the anode current density detected during this period is corrected by the reference electrode as an invention example, and the correction value not corrected is shown as a comparative example in comparison with FIG.
In the initial 5 days after setting the test piece, corrosion at each site has hardly occurred yet, and as shown in FIG. 9, the anode current density of the inventive example was not different depending on the installation site. On the other hand, in the comparative example, a difference in anode current density depending on the installation site was observed. This difference is considered to be the difference between the site where the temperature rose due to daylight (fender) and the site where the temperature did not rise much (under the floor) depending on the installation site.
It can be seen that an accurate anode current density value (permeated hydrogen current density value) can be obtained without being affected by a temperature change by correcting the measured anode current density value by the reference electrode according to the present invention. .

  According to the present invention, the amount of hydrogen generated by corrosion in a corrosive environment in which each part of the metal material constituting the moving body whose environment changes continuously is exposed in use and enters the metal material. Can be continuously and accurately monitored.

DESCRIPTION OF SYMBOLS 1 Electrolysis tank 2 Sample 3 Reference electrode 4 Electrode 4b Counter electrode 5 Sintered glass frit 6 Test object (steel plate)
7 cell 7a reference cell 8 counter electrode 9 reference electrode
10 Protective film

Claims (4)

A method for monitoring the amount of hydrogen entering a metal part of a moving body,
A method for measuring the amount of hydrogen penetrating into the interior of a metal is applied to a metal part to be evaluated of a moving body, at least a part of which is made of a metal material, and the amount of hydrogen penetrating into the metal due to corrosion of the metal part to be evaluated Is continuously measured in a corrosive environment that varies with the traveling environment of the moving body,
A method for measuring the amount of hydrogen penetrating into the metal is
This is a method of measuring the amount of hydrogen generated by corrosion of metal materials and penetrating into the interior of the metal using a multi-channel potentiostat using the electrochemical hydrogen permeation method , and corrodes one side of the metal material as the specimen. In the state where the intrusion surface of hydrogen that is exposed to the environment and generated by a corrosion reaction is used, the other surface of the subject is a hydrogen detection surface, and the potential on the hydrogen detection surface side is maintained at −0.1 to +0.3 V vs. SCE. When measuring the flux of hydrogen diffusing to the detection surface as an anode current,
An electrochemical cell composed of a plurality of cell groups divided into at least two cells is disposed on the hydrogen detection surface side of the same subject, and each cell in the cell group has a pH of 9 to 13 Fill with electrolyte solution and install independent reference electrode and counter electrode,
At least one cell in the cell group is used as a reference cell for correcting the residual current, and a protective film that blocks contact with the corrosive environment is provided at a location corresponding to the hydrogen entry surface side of the reference cell,
Of the hydrogen intrusion surface of the specimen, in a location corresponding to a cell other than the reference cell, the metal material is directly exposed to a corrosive environment without providing a protective film,
An anode current value detected in a cell other than the reference cell is corrected by a residual current value detected in the reference cell, and an intrusion hydrogen amount from the corroded surface side is calculated based on the corrected anode current value. And a method for monitoring the amount of hydrogen entering the metal part of the moving body .
However, the intrusion hydrogen amount (permeated hydrogen amount) is converted according to the following equation.
The value obtained by subtracting the anode current density value detected in the reference cell from the anode current density value detected in a cell other than the reference cell is a permeated hydrogen current density: i _H (μA / cm ² = 10 ⁻⁶ A / cm ² ), The amount of invading hydrogen per unit area: M _H (mol / scm ² ) or m _H (pieces / scm ² )
M _H = i _H × 1.036 × 10 ^-11 (mol / scm ² ),
m _H = i _H x 6.24 x 10 ¹² (pieces / scm ² )
Ask for. The Ir / Ir oxide electrode is used as the reference electrode, The method for monitoring the amount of hydrogen entering the metal part of the moving body according to claim 1. 3. The amount of hydrogen penetrating into the metal part of the moving body according to claim 1, wherein the surface of the specimen on the hydrogen detection surface side is previously coated with Pd, a Pd-containing alloy, or Ni . Monitoring method . The metal of the mobile body according to any one of claims 1 to 3 , wherein the delayed fracture sensitivity of the metal part is evaluated from the amount of hydrogen entering the metal part to be evaluated of the mobile body. How to monitor the amount of hydrogen entering the site.