JP6540596B2 - Method of measuring intruding hydrogen amount and intruding hydrogen amount measuring device - Google Patents

Description

  The present invention relates to a method of measuring the amount of hydrogen invading into the metal due to corrosion (the amount of invading hydrogen) by the electrochemical hydrogen permeation method, and in particular, in a corrosive environment in which the temperature changes (variable temperature environment) The present invention relates to a method of measuring the amount of invading hydrogen which can accurately measure the amount of invading hydrogen by removing the influence of the passive holding current as the background which fluctuates with temperature. The present invention also relates to an apparatus for measuring the amount of intruding hydrogen for performing the method of measuring the amount of intruding hydrogen.

  In recent years, the use of high strength steels has been expanded in all fields from the viewpoint of resource saving and energy saving. However, it is known that the use of high strength steel is also detrimental, and the risk of hydrogen embrittlement increases as the material strength increases (Non-Patent Document 1). In the automotive field, in particular, ultra high strength steel sheets having a tensile strength of 1180 MPa have begun to be used, and such steel sheets are concerned about the occurrence of hydrogen embrittlement even in the atmospheric environment. In the atmospheric environment, hydrogen intrudes into the steel as the corrosion reaction proceeds, and the amount of invading hydrogen also changes due to changes in environmental factors such as temperature, humidity, and salinity. Therefore, in order to grasp the hydrogen penetration behavior in the atmospheric environment, a technique for continuously monitoring the amount of intruded hydrogen is desired.

  In Non-Patent Document 2, based on the electrochemical hydrogen permeation method, one side of a metal as a test piece is exposed to an atmospheric corrosive environment, and hydrogen which has penetrated and permeated into steel is detected on the opposite side of the test piece. The results of monitoring the anode current on the surface have been reported. Here, in the anode current measured by the electrochemical hydrogen permeation method, in addition to the hydrogen permeation current measured in ionizing the hydrogen atoms transmitted in the steel on the detection surface, the passive state as a background Hold current is included. Although this passive state holding current is known to depend on temperature (non-patent document 3), in the method described in non-patent document 2, since this temperature dependency is not considered, hydrogen penetration It is not possible to estimate the quantity accurately.

  Therefore, Patent Document 1 proposes a method of correcting the influence of the passive state holding current in the measurement of the amount of intruding hydrogen by the electrochemical hydrogen permeation method. Specifically, two or more measurement cells are installed on the same test piece, and a protective film is provided on the hydrogen intrusion surface of one of the measurement cells to prevent the penetration of hydrogen, thereby measuring the passive state holding current. The effect of the temperature-dependent passive holding current is removed by subtracting the passive holding current measured in the reference cell from the anode current measured in the normal measuring cell as a reference cell.

JP, 2014-89207, A

Matsuyama Yusaku, "Delayed Destruction", Nikkan Kogyo Shimbun, 1989 Ohmura et al., Iron and Steel, 2005, Vol. 91, no. 5, p. 478-484 Toshio Shibata, Materials and Environment, 2011, Vol. 60, p. 374-379 Muto et al., Materials and Environment, 1998, Vol. 47, p. 519-527 Takahiro Kushida, Materials and Environment, 2000, Vol. 49, p. 195-200

  According to the method described in Patent Document 1, the measurement accuracy of the amount of intruding hydrogen can be improved. However, even if it is the same test piece as a result of examination of the present inventors, a passive state holding current changes with positions, As a result, correction | amendment of a background may become difficult in the method of patent document 1 I found that.

  The present invention has been made in view of the above circumstances, and it is possible to measure the amount of intruding hydrogen accurately and continuously by removing the influence of the passive state holding current even in a corrosive environment where the temperature changes. An object of the present invention is to provide a method of measuring an amount and a measuring device therefor.

  As a result of intensive studies to achieve the above object, the present inventors formulate in advance the temperature dependency of the passive state holding current which is a background current, and use the above-mentioned formula when measuring. By calculating and correcting the passive state holding current value from the temperature of the test environment, it has been found that the amount of intruding hydrogen can be accurately measured even in an environment where the temperature fluctuates.

The present invention has been made based on the above findings, and the summary of the invention is as follows.
1. An intruding hydrogen amount measuring method for measuring the amount of hydrogen entering the inside of a metal by corrosion by an electrochemical hydrogen permeation method in a corrosive environment in which the temperature changes,
One side of the test piece made of metal material is exposed to the corrosive environment to make it a hydrogen intrusion surface,
The other surface of the test piece is a hydrogen detection surface provided with a plating film,
The anode current density: i _a is measured by the electrochemical cell installed on the hydrogen detection surface,
Temperature of test environment: Measure T,
Previously determined, passive holding current density is expressed by the following equation (1): i _p and temperature of the test environment: Based on the relationship between T, the measured temperature of the said test environment: from T passive holding current density: to calculate the i _p,
The anode current density from said i _a passive holding current density by subtracting i _p, the hydrogen permeation current density: seeking i _H,
The hydrogen permeation current density: i calculates the absorbed hydrogen amount from _H, absorbed hydrogen amount measuring method.
Notation i _p = A × e − ^{B / T} (1)
(Here, A and B are constants depending on the properties of the plating film)

2. The method for measuring the amount of intruded hydrogen according to 1 above, wherein the temperature of the test piece is measured as the temperature of the test environment: T.

3. The method for measuring the amount of intruded hydrogen according to the above 1 or 2, wherein the corrosive environment is an outdoor exposure environment exposed to direct sunlight.

4. An intrusion hydrogen amount measurement device for carrying out the intrusion hydrogen amount measurement method described in 2 above,
An electrochemical cell installed on the hydrogen detection surface of the test piece;
Temperature measurement means for measuring the temperature of the test piece;
Control means connected to the electrochemical cell and the temperature measuring means;
The control means
The measurement of anode current density by the electrochemical cell: i _{a and} the measurement of the temperature of the test piece by the temperature measurement means: T at the same time,
Previously determined (1) of the test piece was measured based on a relationship type temperature: T from passive holding current density: calculating a i _p,
The anode current density from said i _a passive holding current density by subtracting i _p, the hydrogen permeation current density: seeking i _H,
The hydrogen permeation current density: from i _H is configured to calculate the absorbed hydrogen amount absorbed hydrogen amount measuring device.

  According to the present invention, even in a corrosive environment in which the temperature changes, the amount of intruding hydrogen can be measured accurately and continuously by removing the influence of the passive state holding current.

It is a schematic diagram which shows the amount measurement system of intrusion hydrogen in one embodiment of the present invention. It is a graph which shows the temperature dependence of the passive state holding | maintenance electric current in a measurement cell and a reference cell. It is a graph which shows the time-dependent change of the anode current in a measurement cell and a reference cell, and a test piece temperature. It is a graph which shows a time-dependent change of the hydrogen permeation current density obtained by the method of an Example and a comparative example.

  In the method of measuring the amount of intrusive hydrogen according to one embodiment of the present invention, the amount of hydrogen entering the inside of the metal due to corrosion is measured by the electrochemical hydrogen permeation method. At that time, one surface of the test piece made of a metal material is exposed to a corrosive environment to be a hydrogen intrusion surface, and the other surface of the test piece is a hydrogen detection surface, the hydrogen permeation flux in the test body is It measures as anode current density using the electrochemical cell installed in the hydrogen detection side.

The anode current density: The i _a, the hydrogen permeation current density is ionization current of the hydrogen atoms has been transmitted through the test piece: In addition to i _H, background current at some passivation holding current density includes i _p The passive holding current density depends on temperature (non-patent document 3). Therefore, in order to measure an accurate hydrogen permeation current in an environment where the temperature changes, it is necessary to perform background correction after taking into consideration the temperature change of the passive state holding current.

  In Patent Document 1, correction is performed by providing a normal measurement cell and a reference cell on the same test piece, and subtracting the passive holding current measured in the reference cell from the anode current measured in the measurement cell. Has been proposed. However, as described above, it has been found that, even with the same test piece, it is difficult to correct the background in the above method because the passive state holding current differs depending on the position.

  Here, the hydrogen detection surface of the test piece used in the electrochemical hydrogen permeation method is generally coated with a plating film such as Ni, Pd, or an alloy thereof, Even on the surface, it is difficult to form a plating film uniformly, and therefore, the properties of the plating film differ depending on the position on the surface of the test piece. It is considered that the difference in the properties of the plated film affects the temperature dependency of the passive state holding current.

  Therefore, in the present invention, the temperature dependency of the passive state holding current is measured in advance and made into a mathematical expression, and background correction at the time of measurement is performed using the above-mentioned mathematical expression. Thus, correction can be performed based on the temperature measurement result of the test environment without separately providing a reference cell for measurement.

Hereinafter, the correction method in the present invention will be specifically described.
Passive holding current density: i _p denotes a linear relationship that logarithm is against the reciprocal of temperature, it is known to satisfy the Arrhenius equation. Therefore, first, in an environment where hydrogen does not penetrate, that is, an environment where the test piece does not corrode, the temperature of the test environment is changed to measure the passive holding current density, and the passive holding current density is the temperature as in the following formula (1) Formulate as a function of
i _p = A × e ^{−B / T} (1)
Here, A and B in the equation (1) are constants depending on the properties of the plating film and the like, and T is the absolute temperature (K) of the test environment.

  Here, the mathematical expression, that is, the determination of A and B can be performed in any environment as long as the test piece is not corroded. An example of an environment in which the test piece does not corrode is a low humidity environment with no salt attached to the hydrogen intrusion surface. In this case, the humidity is preferably 30% RH or less. Moreover, it can replace with setting it as low humidity, and can also provide the protective film which prevents corrosion of this test piece in the hydrogen penetration | invasion surface of a test piece. The protective film is preferably one that can be peeled off without changing the surface state of the hydrogen penetration surface of the test piece. For example, a protective film made of a resin can be used as the protective film, and an epoxy resin-based paint or the like can be used as the resin.

In the measurement of the actual hydrogen penetration amount, the temperature of the test environment: T is measured, and the temperature of the test environment obtained: From the value of T and the above equation (1), the passive holding current density at that temperature: i calculate the _p, anode current density is measured by electrochemical hydrogen permeation method: i _a a passive holding current density: i by subtracting the _p, net hydrogen permeation current density: i _H can be obtained ( The following (2) formula. The units of i _H , i _a , and i _p are not particularly limited, and the calculation of the equation (2) holds true for the same unit, but can be, for example, A / cm ² .
i _H = i _a −i _p (2)

  As the temperature of the test environment, the temperature of the environment in which the test piece is placed can be used. However, for example, in the case where the amount of invading hydrogen is measured in an outdoor exposure environment, the temperature of the test environment and the temperature of the test piece may be different due to the influence of direct sunlight, radiation cooling and the like (Non-patent Document 4). Therefore, more accurate measurement of hydrogen permeation current density becomes possible by measuring the temperature of the test piece as the temperature of the test environment.

The amount of hydrogen penetration can be calculated from the hydrogen permeation current density obtained as described above. Here, the amount of invading hydrogen in the electrochemical hydrogen permeation method is calculated as surface hydrogen concentration (adsorbed hydrogen concentration on the hydrogen intrusion surface): C _ab , and calculated by the following (3) formula using hydrogen permeation current: i _H Be done.
C _ab = (i _H × L × M _H ) / (D × F × d) × 10 ⁶ (3)
C _ab : surface hydrogen concentration (mass ppm)
i _H : Hydrogen permeation current density (A / cm ² )
L: Thickness of test piece (cm)
D: Hydrogen diffusion coefficient in the metal material of the test piece (cm ² / s)
F: Faraday constant (C / mol)
M _H : molar mass of hydrogen atom (g / mol)
d: Density of metal material of test piece (g / cm ³ )

  In an environment where the temperature changes, the hydrogen diffusion coefficient D in the material changes. The hydrogen diffusion coefficient is also known to satisfy the Arrhenius equation, whose logarithmic value shows a linear relationship with the reciprocal of temperature as well as the passive state holding current, and hydrogen diffusion is previously carried out by using the apparatus of the present invention. By formulating the temperature dependency of the coefficient, it is possible to calculate the temperature change of the hydrogen diffusion coefficient from the material temperature of the test body and calculate the amount of intruding hydrogen more accurately.

  As described above, according to the present invention, even in a corrosive environment where temperature changes, the amount of intruding hydrogen can be measured accurately and continuously by removing the influence of the passive holding current without separately providing a reference cell. it can. Therefore, it is possible to accurately measure the amount of intruding hydrogen which changes momentarily in a corrosive environment.

  Next, the apparatus for measuring the amount of intruded hydrogen according to the present invention will be described. The apparatus for measuring the amount of intruding hydrogen according to the present invention is connected to an electrochemical cell installed on a hydrogen detection surface of a test piece, temperature measurement means for measuring the temperature of the test piece, the electrochemical cell and the temperature measurement means Control means.

  FIG. 1 is a schematic view showing an intrusion hydrogen amount measuring apparatus 1 according to an embodiment of the present invention. One side of the test piece 10 is exposed to a corrosive environment to be a hydrogen intrusion surface 11, and the other side of the test piece is a hydrogen detection surface 12. The hydrogen detection surface 12 is provided with a plating film not shown. Further, an electrochemical cell 20 for measuring an anode current is installed on the hydrogen detection surface 12.

  Although any test piece made of a metal material can be used as the test piece 10, a plate-like steel plate is used in the example shown in FIG. The thickness of the test piece 10 is not particularly limited, and can be any thickness. However, if the test piece is too thick, the time delay between the change in the corrosive 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 intruded hydrogen is unclear It may be Therefore, in particular, when the hydrogen diffusion coefficient of the material constituting the test piece is small, it is preferable to reduce the plate thickness. In addition, it is preferable that the plate thickness be as thin as possible because accurate calculation of the surface hydrogen concentration can not be performed if hydrogen diffusion in the material is not steady. Specifically, the thickness of the test piece is preferably 1 mm or less, and more preferably 0.5 mm or less. On the other hand, if the test piece is excessively thin, corrosion may occur in a short period of time, so the thickness of the test piece is preferably 0.2 mm or more.

  Any electrochemical cell can be used as long as it can measure the anode current at the hydrogen detection surface 12. In the example shown in FIG. 1, the electrochemical cell 20 includes an electrolytic solution 21, a container 22 for containing the electrolytic solution 21, a reference electrode 23 disposed inside the container 21, and a counter electrode 24. ing.

  As the electrolyte solution 21, any solution can be used as long as it can measure the anode current, but usually, an electrolyte aqueous solution is used. Further, if the pH of the electrolyte solution 21 is less than 9, it may be difficult to maintain the passive state on the hydrogen detection surface 12 at the time of anode current measurement, so the pH of the electrolyte solution 21 should be 9 or more preferable. On the other hand, if the pH is excessively high, that is, it is strongly alkaline, if the electrolyte leaks to the outside due to an accident or the like, the pH of the electrolyte may be 13 or less because the damage to the environment is large. preferable. As an electrolyte solution which satisfy | fills the said conditions and can be used suitably, the NaOH aqueous solution of about 0.1-1.0 M (M = mol / L) grade is mentioned, for example. In addition, it is preferable to use a gel electrolyte instead of the liquid electrolyte from the viewpoint of the prevention of leakage of the electrolyte and the ease of handling.

  Although any container can be used as the container 22 as long as it can store the electrolyte solution 21 etc., a container made of insulating glass, resin or the like is usually used. In particular, in terms of processability and handling ease, it is preferable to use a resin, and more preferable to use an acrylic resin.

  The reference electrode 23 is an electrode serving as a reference of the potential when measuring the anode current in the electrochemical cell 20, and is also referred to as a reference electrode. The reference electrode 23 is not particularly limited, and various types of electrodes currently in practical use such as those used for general electrochemical measurement can be used. An example of a reference electrode that can be suitably used is a silver-silver chloride electrode (SSE). As an aqueous electrolyte solution used for the silver-silver chloride electrode, for example, saturated KCl or the like can be used.

  As the counter electrode 24, any inert electrode can be used as long as it can measure the anode current and does not inhibit the ionization reaction of hydrogen atoms on the hydrogen detection surface 12. Examples of counter electrodes that can be suitably used include platinum (Pt) electrodes.

  The reference electrode 23 and the counter electrode 24 are connected to the potentiostat 30. Moreover, the test piece 10 is also connected to the potentiostat 30, and becomes a working electrode at the time of anode current measurement.

  Furthermore, in the example shown in FIG. 1, a thermocouple 40 as a temperature measurement means for measuring the temperature of the test piece 10 is placed in contact with the test piece 10. As the thermocouple 40, any one can be used, such as a general thermocouple as represented by alumel-chromel (K thermocouple). Although the method of installing the thermocouple is not particularly limited, it is preferable to cover the portion where the test piece and the thermocouple are in contact from the viewpoint of preventing the dissimilar metal contact corrosion between the test piece and the thermocouple.

The apparatus for measuring the amount of intruding hydrogen according to the present invention is provided with a control means, and the control means measures the anode current density: i _a by the electrochemical cell, and the temperature of the test piece by the temperature measurement means: T perform measurements simultaneously, previously obtained (1) of the test piece was measured based on a relationship type temperature: T from passive holding current density i _p is calculated, and the anode current density from said i _a by subtracting the i _p, the hydrogen permeation current density: passive holding current density seek i _H, the hydrogen permeation current density is from i _H is configured to calculate the absorbed hydrogen amount. In the example shown in FIG. 1, the potentiostat 30 and the temperature logger 50 can also be considered as part of the control means.

  The measurement conditions in the present invention are not particularly limited as long as they are a combination of a solution and a potential capable of maintaining the passive state of the surface of the steel when the potential is sufficient for the ionization reaction of hydrogen on the hydrogen detection surface. It is not a thing. Generally, -0.1 to 0.3 V vs. 1 N aqueous NaOH solution. The polarization condition of SCE is widely used (non-patent document 3). Here, SCE refers to a saturated calomel electrode, and the potential of this SCE relative to a standard hydrogen electrode (SHE) is indicated by +0.244 V (vs SHE, 25 ° C.). Moreover, when SSE is used, it can measure at 0 V (nonpatent literature 5).

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

(Example)
Using a mild steel plate having a thickness of 1 mm as a test piece, the amount of intruding hydrogen was measured under the conditions described below with the apparatus having the configuration shown in FIG. The hydrogen detection surface of the test piece was plated with Pd to a thickness of about 100 nm. As an electrolyte, 1N NaOH is used, 0 V vs. Anodic polarization was performed under SSE conditions.

(Comparative example)
Also, for comparison, the method of Patent Document 1 is simulated, and a reference cell for background correction is disposed on the hydrogen detection surface of the same test piece as the above embodiment, and the reference cell corresponding to the hydrogen intrusion surface is supported. The coating was covered with a protective film. Hereinafter, the electrochemical cell in the above embodiment is referred to as "measurement cell", and the electrochemical cell in the comparative example is referred to as "reference cell". The measurement conditions in the reference cell were the same as the measurement cell except that the protective film was provided as described above.

[Temperature dependence of passive holding current density]
Prior to the measurement of the amount of intruding hydrogen, the temperature retention of the passive holding current density in the measurement cell and the reference cell was evaluated.

  In order to measure the passive state holding current density, it is necessary to measure the current without hydrogen penetration on the hydrogen penetration surface. The hydrogen intrusion surface of the reference cell is covered with a protective film, but there is no protective film on the hydrogen intrusion surface of the measurement cell. Therefore, to measure the passive holding current density in the measurement cell, the hydrogen intrusion surface of the measurement cell It is necessary to prevent corrosion in the Therefore, the current was measured in a low humidity environment (30% RH) without salt adhesion to the hydrogen intrusion surface of the test piece. The current measured in this state can be regarded as a passive state holding current because it does not include a hydrogen permeation current in either the measurement cell or the reference cell.

FIG. 2 is a graph showing the temperature dependency of the passive state holding current in the measurement cell and the reference cell measured by the above method. Here, the temperature of the test piece was changed to 20, 30, 40 and 50 ° C. to measure the holding current. It can be seen from FIG. 2 that there is a linear relationship between the logarithmic value of the passive current density and the reciprocal of the temperature, and the Arrhenius equation holds. From the above results, the temperature dependence of the passive current density in the measurement cell and the reference cell can be mathematically expressed as follows.
Measuring ^{_{cell: i p (nA / cm 2}} ) = 1.124 × 10 13 × exp (-8.038 × 10 3 / T) ... (4)
Reference ^{_{cell: i p (nA / cm 2}} ) = 2.455 × 10 13 × exp (-8.164 × 10 3 / T) ... (5)
In addition, comparing the passivity holding current density at each temperature between the reference cell and the measurement cell, the passivity holding current value density of the reference cell is larger than that of the measurement cell, and the passivity is different if the measurement location is different even in the same test body. It can be seen that the holding current density is different.

[Measurement of hydrogen permeation current density]
Next, the test piece was exposed to an outdoor environment, and the anode current and the temperature of the test piece were simultaneously measured. FIG. 3 is a graph showing temporal changes in anode current density and test piece temperature in the measurement cell and the reference cell. From the measurement results, it can be seen that the anode current density fluctuates under the influence of temperature change in both the reference cell and the measurement cell.

  Here, in accordance with the method of Patent Document 1, in order to remove the passive current which is the background current, the result of subtracting the current density in the reference cell from the anode current density measured in the measurement cell is shown in FIG. It shows as a comparative example (broken line). In the comparative example, the hydrogen permeation current value density shows a negative value in most of the measurement period. This is considered to be the result of excessive removal of the background current due to the difference in passivation current between the measurement cell and the reference cell. Therefore, even if it is the same test object, when the temperature dependence of a passive current is different by the location to measure, it turns out that temperature correction by the method proposed by patent documents 1 is difficult.

  On the other hand, the passive state holding current density is calculated from the above-mentioned equation (4) representing the temperature dependency of the passive state holding current density in the measuring cell and the measured value of the test piece temperature shown in FIG. The hydrogen transmission current density was determined by subtracting the current density from the anode current density in the measurement cell shown by the solid line in FIG. 3, and the result is shown as an example of the present invention (solid line) in FIG. From the results shown in FIG. 4, it can be seen that according to the present invention, even in a corrosive environment in which the temperature changes, the influence of the passive holding current can be removed to evaluate the amount of intruding hydrogen accurately and continuously.

  As described above, according to the present invention, it is possible to measure the amount of hydrogen entering the metal material continuously with high accuracy in a corrosive environment in which the temperature fluctuates. Therefore, by using the present invention, the correlation between the environmental factor and the amount of intruding hydrogen can be accurately grasped, and it is extremely effective for judging the applicability of metallic materials including ultra-high strength steel to the atmospheric environment. is there.

DESCRIPTION OF SYMBOLS 1 intrusion hydrogen amount measuring apparatus 10 test piece 11 hydrogen intrusion surface 12 hydrogen detection surface 20 electrochemical cell 21 electrolyte solution 22 container 23 reference electrode 24 counter electrode 30 potentiostat 40 thermocouple (temperature measurement means)
50 temperature logger

Claims (3)

An intruding hydrogen amount measuring method for measuring the amount of hydrogen entering the inside of a metal by corrosion by an electrochemical hydrogen permeation method in a corrosive environment in which the temperature changes,
One side of the test piece made of metal material is exposed to the corrosive environment to make it a hydrogen intrusion surface,
The other surface of the test piece is a hydrogen detection surface provided with a plating film,
The anode current density: i _a is measured by the electrochemical cell installed on the hydrogen detection surface,
Measure the temperature of the test piece as T: the temperature of the test environment,
The test piece was calculated in advance in an environment that does not corrode, passive holding current density is expressed by the following equation (1): i _p and temperature of the test environment: Based on the relationship between T (K), measured the temperature of the test environment: T from passive holding current density: calculating a i _p,
The anode current density from said i _a passive holding current density by subtracting i _p, the hydrogen permeation current density: seeking i _H,
The hydrogen permeation current density: i calculates the absorbed hydrogen amount from _H, absorbed hydrogen amount measuring method.
Notation i _p = A × e − ^{B / T} (1)
(Here, A and B are constants depending on the properties of the plating film) The method for measuring the amount of intruded hydrogen according to claim 1, wherein the corrosive environment is an outdoor exposure environment exposed to direct sunlight. An intrusion hydrogen amount measurement apparatus for carrying out the intrusion hydrogen amount measurement method according to claim 1 , wherein
An electrochemical cell installed on the hydrogen detection surface of the test piece;
Temperature measurement means for measuring the temperature of the test piece;
Control means connected to the electrochemical cell and the temperature measuring means;
The control means
The measurement of anode current density by the electrochemical cell: i _{a and} the measurement of the temperature of the test piece by the temperature measurement means: T at the same time,
Previously determined (1) of the test piece was measured based on a relationship type temperature: T from passive holding current density: calculating a i _p,
The anode current density from said i _a passive holding current density by subtracting i _p, the hydrogen permeation current density: seeking i _H,
The hydrogen permeation current density: from i _H is configured to calculate the absorbed hydrogen amount absorbed hydrogen amount measuring device.

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