JP2013044712A - Method for measuring amount of hydrogen penetrated into metal and method for monitoring amount of hydrogen penetrated into metal portion of moving body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for accurately measuring an amount of hydrogen penetrated into metal having a coating formed thereon in different conditions.SOLUTION: A method for measuring an amount of hydrogen penetrated into metal, includes: setting one side of a specimen to a penetration surface of hydrogen generated by a corrosion action due to exposure to a corrosive environment, and the other side thereof to a detection surface of hydrogen; measuring a hydrogen flux diffused to the detection surface as an anode current; disposing an electrochemical cell formed by a plurality of cell groups on the hydrogen detection surface side of the specimen; filling an electrolyte aqueous solution of pH 9-13 into each cell of the cell groups; independently placing a reference electrode and an opposite electrode; setting at least one cell of the cell groups to a reference cell for correcting a residual current; providing a protective film for blocking contact with the corrosive environment in a place corresponding to the hydrogen penetration surface side of the reference cell; correcting an anode current value detected in a cell except the reference cell by a residual-current value detected by the reference cell; and calculating a hydrogen amount penetrated from the corrosion surface side on the basis of the corrected anode current value.

Description

The present invention relates to a method for measuring the amount of hydrogen penetrating into a metal, which can accurately measure the amount of hydrogen penetrating into the metal on which a coating of various conditions is formed as it corrodes.
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 that in a delayed fracture property evaluation method for evaluating delayed fracture characteristics of a steel material by making the steel material contain diffusible hydrogen by cathodic charging and measuring the critical diffusible hydrogen content, 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.

  Non-Patent Document 2 reports a method for evaluating the amount of hydrogen penetration using ammonium thiocyanate. In this document, a comparison is made between the hydrogen penetration amount obtained by ammonium thiocyanate and the hydrogen penetration amount obtained by the cathodic charging method.

  Furthermore, Non-Patent Document 3 reports an example in which a high-strength bolt that has been corroded for a certain period of time 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 4).

JP-A-2005-134152

"Matsuyama Junsaku: Delayed Destruction, Nikkan Kogyo Shimbun, Tokyo, (1989)" "Omura et al .: Corrosion and corrosion symposium materials, Vol.170, p.47-54 (2010)" “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)"

  In the technique described in Patent Document 1, since the hydrogen intrusion into the steel is an accelerated test in which hydrogen is forcibly intruded by cathodic charging, under the conditions different from the actual usage environment, Although it is possible to give a superiority or inferiority to the occurrence of delayed fracture depending on the type, it is not a judgment material for estimating whether or not delayed fracture occurs due to the amount of hydrogen intrusion due to corrosion in the actual use environment.

In addition, the method for evaluating the amount of hydrogen intrusion using ammonium thiocyanate shown in Non-Patent Document 2 is not a judgment material for estimating whether or not delayed fracture occurs due to the amount of hydrogen intrusion associated with surface corrosion. .
Furthermore, the data obtained by the atmospheric exposure test disclosed in Non-Patent Document 3 are merely test results under environmental factors associated with the topographic 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 shown in Non-Patent Document 3 to the external environment, the change in the residual current on the anode side due to 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.

  Also, when high-strength steel parts are used in automobiles, etc., for the purpose of improving corrosion resistance, galvanized or heat-treated alloyed galvanized steel is applied to steel with increased strength. For the purpose of obtaining an aesthetic appearance, the steel material is subjected to various coatings. In this case, even if the parts are made of the same steel material, the degree of corrosion varies greatly depending on the type and coverage of the coating, and as a result, the amount of hydrogen intrusion due to the corrosion also varies greatly. Therefore, it has been desired to develop a technology capable of accurately grasping the hydrogen penetration amount of a metal material having a coating formed under various conditions.

The present invention has been developed in view of the above-mentioned present situation, and by taking into account the change in the residual current on the anode side accompanying the temperature change of the environment, the inside of the metal having a coating under various conditions accompanying corrosion. The object is to propose a method for measuring the amount of hydrogen penetrating into a metal, which can accurately measure the amount of penetrating hydrogen.
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 measuring the amount of hydrogen generated by corrosion of a metal material and penetrating into the metal by using an electrochemical hydrogen permeation method, with a coverage of 30% on one surface of a specimen made of a metal material The surface treated surface with a coating of less than 100% is exposed to a corrosive environment and used as a hydrogen intrusion surface generated by a corrosion reaction, while the other surface of the specimen is used as a hydrogen detection surface, When measuring the flux of hydrogen diffusing on the detection surface with the potential held at −0.1 to +0.3 V vs. SCE as the 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 analyte, and an electrolyte having a pH of 9 to 13 is provided inside each cell of the cell group. Fill with aqueous solution and install independent reference electrode and counter electrode,
At least one cell in the cell group serves as a reference cell for correcting a residual current, and a protective film that blocks contact with a corrosive environment is provided at a location corresponding to the hydrogen intrusion surface side of the reference cell,
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. A method for measuring the amount of hydrogen penetrating into a metal.

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

3. 3. The method for measuring the amount of hydrogen penetrating into a metal according to 1 or 2 above, wherein the surface of the specimen on the hydrogen detection surface side is previously coated with Pd or a Pd-containing alloy or Ni.

4). The method for measuring the amount of invading hydrogen according to any one of 1 to 3 is applied to a metal part to be evaluated of a moving body, at least part of which is made of a metal material, A method for monitoring the amount of hydrogen invading into a metal part of a moving body, wherein the amount of hydrogen intruding into the body is continuously measured in a corrosive environment that varies with the traveling environment of the moving body.

5). 5. The amount of hydrogen invading into the metal part of the mobile body according to the item 4, wherein the delayed fracture sensitivity of the metal part is evaluated from the amount of hydrogen intruding into the metal part to be evaluated of the mobile body. Monitoring method.

According to the present invention, it is possible to accurately detect the amount of hydrogen penetrating into the inside of a metal having a coating under various conditions 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 a figure for demonstrating an appropriate plating state when the corrosion part is plated in stripes, (a) shows an appropriate plating state, (b) shows an inappropriate plating state. 1 is a diagram schematically showing a cell structure used in Example 1. FIG.

  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 and airplanes. Hereinafter, embodiments will be described in detail with reference to automobiles as representative examples. explain. The metal material to be evaluated is not necessarily limited to steel, but here, a case where it is applied to steel will be described as a representative example.

  The present invention measures the amount of hydrogen that is generated due to corrosion of a metal material and enters 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 5). 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 the hydrogen diffusion coefficient in steel”.
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 a main component of the residual current, and is influenced by various factors, but it varies particularly 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, and 7d are provided on the hydrogen detection surface side of the steel material 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 material 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 material 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.

  Also, in the present invention, paying attention to the fact that the amount of hydrogen entering the steel changes significantly due to changes in the coating conditions such as plating formed on the steel material, the amount of hydrogen entering the steel material having the coating is calculated. It is characterized by doing. In the conventional method for measuring the amount of intrusion hydrogen, since the amount of intrusion hydrogen was measured using a steel material on which no coating was formed, there was a possibility that it was erroneous to determine whether delayed fracture had occurred. Since the amount of intrusion hydrogen is measured using steel materials having coatings of various conditions, it is possible to accurately determine the occurrence of delayed fracture. Here, the coating conditions refer to the type of coating and the coverage.

Hereinafter, the present invention will be specifically described.
In the present invention, in order to keep the steel material 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 at a predetermined 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 0.2M NaOH aqueous solution, and the steel surface of the hydrogen detection surface is maintained at a potential sufficient for the ionization reaction of hydrogen. Any electrolyte solution may be used as long as it can ensure a passivated state of the surface of the steel material. 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 a chloride-containing electrode such as an Ag / AgCl electrode, contamination of the anode electrode chamber solution with chloride ions 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 (IrOx) 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 steel material as the detection body has a coating, and the coverage is in the range of 30% to less than 100%. Here, the type of the coating is not particularly limited and may be formed on the surface of the steel material, and the thickness may be 1/10 or less of the thickness of the steel material. For example, zinc-based plating, plating such as Al-based plating, phosphate compounds, organic resin coatings, and the like can be given.

  The corrosion of a steel material having a coating in an atmospheric corrosive environment will be described using a commonly used zinc-based plating as an example. When galvanized steel sheet is exposed to atmospheric corrosive environment, first, galvanic corrosion occurs (period 1), then galvanic corrosion reaches the base steel, and galvanic corrosion between zinc and base steel Occurs (period 2). Thereafter, there is a corrosion prevention period due to the corrosion product of zinc (period 3), and the corrosion of the base steel material occurs due to the loss of this corrosion product (period 4). In the present invention, when the period in which the type of the surface coating affects hydrogen intrusion is considered, it is considered that the period 2 to 4 corresponds to it. The measurement of the hydrogen penetration amount in the above periods 2 and 3 is to evaluate the hydrogen penetration characteristic due to the interaction between the steel material and the coating. The measurement of the hydrogen penetration quantity in the above period 4 is in addition to the hydrogen penetration characteristics of 2 and 3. Thus, the hydrogen penetration characteristics due to the corrosion of only the steel material in a state where a part of the coating is completely peeled off will be evaluated. In period 1, since the steel material is covered with 100% coating, it is considered that the base steel material does not corrode and does not enter hydrogen due to corrosion.

Further, the coverage of the coating needs to be in the range of 30% or more and less than 100%. Here, the coverage means the area ratio (%) occupied by the coating when the surface of the coated steel material is viewed from above.
The reason why the coverage is 30% or more is that when it is less than 30%, the effect of forming the coating is small, and the hydrogen penetration amount is the same as the hydrogen penetration amount of the steel material without the coating. This is because it is not possible to obtain sufficient. On the other hand, when the coverage is 100%, the steel material does not corrode as described above, and hydrogen does not enter due to the corrosion. Therefore, the coverage is less than 100%.

  The method for bringing the coating into a desired range is not particularly limited. A steel material with a coating having a desired coverage can be used, or a steel material with a coverage of 100% is processed to form a coating having a desired desired coverage. Is also possible. The method for adjusting the coverage is not particularly limited. For example, coating removal by laser irradiation, melting using an acid or alkali, or mechanical grinding can be mentioned. In addition, after forming a coating with a coverage of 100%, the coating can be cracked and adjusted to a desired coverage by applying a tensile process or a cylindrical deep drawing process.

The distribution of the coating is preferably as uniform as possible. Even if the above-mentioned coverage (30% or more and less than 100%) is satisfied, if there is an extremely uneven coating, the amount of corrosion of the base steel material will increase, and the same intrusion hydrogen as when the coating is not formed This is because there is a possibility that the delayed delayed fracture characteristics cannot be evaluated accurately.
For example, as shown in FIG. 5, when the corroded portion 11 is plated in a striped pattern, as shown in FIG. 5 (a), a certain covering portion 12a with respect to the major axis L of the corroded portion. It is preferable that the ratio of the distance M to the covering portion 12b that is closest thereto is 0.3 or less (M1 / L ≦ 0.3). As shown in FIG. 5 (b), when the above ratio exceeds 0.3 (M2 / L> 0.3), the coatings 12c and 12d are formed unevenly, and the hydrogen penetration amount due to corrosion tends to increase extremely. It is high and there is a risk that accurate delayed fracture characteristics cannot be evaluated.

The area of the corroded portion is not particularly limited, but is preferably in the range of 0.1 to 30 cm ² . If it is less than 0.1 cm ^2, since the anode current value measured is smaller, the ability of the electrochemical measuring device is not preferable because the error increases, when 30 cm ² greater than occur deviation of corrosion in a corrosive surface Since it becomes easy, it is not preferable. Here, the area of the corroded portion is not the total area of the corroded portions but the area of one of the corroded portions in the steel material.
Further, the thickness of the steel plate is not particularly limited, but if it becomes too thick, the anode current value becomes small and the measurement error tends to increase. Therefore, the thickness is preferably 2 mm or less. When it is thin, it is not particularly limited. However, when the plate penetrates due to corrosion, there is a concern about leakage of the internal solution.

  The surface of the hydrogen detection surface of the steel material 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, and Ni. Is mentioned. 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 large and the residual current can be reduced compared to Ni.

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 via an organic adhesive.

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 mobile objects are delayed in destruction due to the amount of hydrogen intrusion due to corrosion in their actual use environment.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

(Example 1: Samples 1 to 9)
(1) Processing of steel plates The steel plates used were commercial mild steel (thickness: 0.8mm) and commercial 1470MPa grade steel, and after processing, sheared to 40 x 50mm and polished on both sides to # 2000 Went. Next, in order to remove a processed layer formed at the time of polishing, both surfaces were subjected to chemical polishing of about 60 μm with an aqueous solution made of a mixed solution of hydrofluoric acid and hydrogen peroxide.
Thereafter, Ni plating of about 100 nm was performed on one side A of the steel plate using a watt bath.
Thereafter, the corroded surface B of the steel sheet was subjected to a surface treatment under the following conditions.
Condition A: A zinc plating film was formed by applying a current of 10 A / dm ² using a solution containing 150 g / L of zinc sulfate heptahydrate.
As a method of adjusting the coverage of the formed galvanized film, a method of adjusting the coverage by applying a tape seal on the steel plate before forming the plating and peeling off the tape after forming the plating to create an uncovered portion (conditions) A-1), a method in which plating is uniformly formed on a steel plate and the coverage is 100% (Condition A-2), or a hydrochloric acid aqueous solution diluted to 5% by applying a tape seal after forming the plating uniformly It was carried out by a method (A-3) in which a coating-free part was prepared by dissolving the plating by using and adjusting the coverage.
Condition B: A nickel plating film was formed by applying current at a current density of 1 A / dm ² using a solution containing 1000 g / L of nickel sulfate hexahydrate.
As a method of adjusting the coverage of the formed nickel plating film, a method of adjusting the coverage by applying a tape seal on the steel plate before forming the plating and removing the tape after forming the plating to create an uncoated portion (conditions) B-1) or a method (B-2) of adjusting the coverage by performing mechanical grinding using # 800 abrasive paper after uniformly forming the plating.
Table 1 shows the types of surface treatment, the conditions for adjusting the coverage, and the coverage of each sample.

(2) Measurement of hydrogen penetration amount The steel plate subjected to the above processing was placed in the cell shown in FIG. The hydrogen detection surface side (single surface A) is filled with 0.1N sodium hydroxide aqueous solution, the reference electrode is Ir / IrOx electrode, the counter electrode is Pt wire, the potential is set to 0V, and the cell is placed in the corrosive environment did. In the corrosion test, an aqueous sodium chloride solution was dropped onto the corroded surface as chloride ions to 1000 mg / m ^3, and the cell was placed in a constant humidity chamber having a humidity of 30%. Thereafter, pure water was dropped every 24 hours from the dropping of salt water, and repeated for a maximum of 5 days to measure the hydrogen penetration amount (ppm) due to corrosion.
In each measurement, a cell that does not corrode was installed to correct the temperature change, and the measurement error before and after the temperature correction was measured. Measurement was performed three times, and the average value of the current density maximum values on the hydrogen detection side was calculated. Table 1 shows the deviation rate (%) of the maximum or minimum value from the average current density value on the hydrogen detection side on the average of 3 times. Furthermore, the amount of hydrogen intrusion was obtained by converting the obtained hydrogen current-side current density, plate thickness, and diffusion coefficient into a hydrogen concentration using Formula 1. The obtained results are shown in Table 1. Furthermore, the current density (μA / cm ² ) relative to the corrosion area was also calculated. Here, the corrosion area indicates an area where no coating is formed.

Conversion of the hydrogen intrusion amount follows the following formula.
Hydrogen penetration amount C = (current density x plate thickness) / hydrogen diffusion coefficient x 1.318

Comparing the deviation rate before and after temperature correction in Table 1, it can be seen that the deviation rate after temperature correction is 10% or less, and that accuracy is greatly improved by performing temperature correction.
Moreover, about the samples 2-7, although the coverage of galvanization was changed, it turns out that the amount of hydrogen penetration | invasion is so high that a coverage is high. This is presumably because when the coverage ratio is high, the area of the anode is relatively larger than that of the cathode at the time of corrosion, and the current value per unit area at the cathode portion is high. Furthermore, for sample 5 with a coverage of less than 30%, the current value for the corroded area is small and close to the value of sample 1 with no coating. It is unknown, and it can be seen that the measurement method according to the present invention is effective when the coverage is 30% or more. Sample 7 is completely covered with plating, and the corrosion area is 0. Therefore, the current value cannot be described in Table 1, but the maximum current value obtained during the test period is plated. When calculated from the corrosion area including the surface, it was 0.03 μA / cm ² . Since the calculation formula is different, it cannot be compared with the results in Table 1 in general, but it can be seen that the value is remarkably lower than those of other examples of galvanization. This is because, in the observation of the corroded portion during the test period, only a corrosion product of zinc, so-called white rust, was observed, and iron rust was not confirmed. From this, it is considered that the state where the iron surface was completely covered with zinc was continued during the test period, and this zinc layer prevented hydrogen from entering the steel sheet. In this way, when the plating layer is completely covered, it is assumed that the hydrogen penetration characteristics of the coating itself can be obtained, but this affects the hydrogen penetration characteristics associated with the corrosion of the steel material subjected to the surface treatment which is the object of the present invention. The effect is not known.
Furthermore, for samples 8 and 9 subjected to nickel plating, both the hydrogen concentration and the current value with respect to the corrosion area are smaller than those of samples 1 to 7 for zinc plating, and nickel plating is performed. It can be seen that hydrogen penetration into the steel sheet can be reduced more effectively.

(Example 2: Samples 10 to 13)
(1) Processing of steel plate After processing using commercial mild steel (thickness: 0.8mm) and commercial 1470MPa grade steel, it was sheared to 40 x 50mm, and both sides were polished to # 2000. Next, in order to remove a processed layer formed at the time of polishing, both surfaces were subjected to chemical polishing of about 60 μm with an aqueous solution made of a mixed solution of hydrofluoric acid and hydrogen peroxide.
Thereafter, Pd plating of about 100 nm was performed on one side A of the steel plate using a commercial K-pure palladium plating bath.
Thereafter, the corroded surface B of the steel sheet was subjected to a surface treatment under the following conditions.
Condition A: A zinc plating film was formed by applying a current of 10 A / dm ² using a solution containing 150 g / L of zinc sulfate heptahydrate. For adjusting the coverage of the formed galvanized film, the coverage is adjusted by adjusting the coverage by applying a tape seal on the steel plate before forming the plating, and then removing the tape after forming the plating to create an uncoated part. Made by adjusting method.
Condition B: A nickel plating film was formed by applying current at a current density of 1 A / dm ² using a solution containing 1000 g / L of nickel sulfate hexahydrate. The coverage of the formed nickel plating film was adjusted by applying a tape seal on the steel plate before forming the plating, and removing the tape after forming the plating to create an uncovered part to adjust the coverage. .
Table 2 shows the type coverage of the surface treatment of each sample.
(2) Measurement of hydrogen intrusion amount in the state of being mounted on the vehicle body A measuring device with 4 cells (CH1 to 4) having a structure as shown in FIG. In the state of being placed under the floor (the lower surface of the floor), it ran for 38 days in the steelworks of JFE Steel Corporation in Fukuyama City, Hiroshima Prefecture. Table 2 shows the results of current values with respect to the amount of hydrogen intrusion and corrosion area on the hydrogen detection side detected during this period.

From the results in Table 2, it was found that the higher the plating coverage, the more the hydrogen penetration due to the corrosion of the steel sheet could be suppressed. Further, it was found that nickel plating has a smaller hydrogen penetration amount than zinc plating, and can suppress corrosion of the steel material and further reduce hydrogen penetration.
Therefore, it becomes possible to determine for each part whether or not delayed fracture occurs due to corrosion in the traveling environment of the actual vehicle.

  According to the present invention, a moving body whose environment changes continuously is generated along with corrosion in a corrosive environment where each part of the metallic material constituting the moving body is exposed in use, and enters the metallic material having a coating. The amount of hydrogen can be monitored continuously and accurately.

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 11 corroded part 12 coating (plating)

Claims (5)

A method for measuring the amount of hydrogen generated by corrosion of a metal material and penetrating into the metal by using an electrochemical hydrogen permeation method, with a coverage of 30% on one surface of a specimen made of a metal material The surface treated surface with a coating of less than 100% is exposed to a corrosive environment and used as a hydrogen intrusion surface generated by a corrosion reaction, while the other surface of the specimen is used as a hydrogen detection surface, When measuring the flux of hydrogen diffusing on the detection surface with the potential held at −0.1 to +0.3 V vs. SCE as the 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 analyte, and an electrolyte having a pH of 9 to 13 is provided inside each cell of the cell group. Fill with aqueous solution and install independent reference electrode and counter electrode,
At least one cell in the cell group serves as a reference cell for correcting a residual current, and a protective film that blocks contact with a corrosive environment is provided at a location corresponding to the hydrogen intrusion surface side of the reference cell,
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. A method for measuring the amount of hydrogen penetrating into a metal.   2. The method for measuring the amount of hydrogen penetrating into a metal according to claim 1, wherein an Ir / Ir oxide electrode is used as the reference electrode.   The method for measuring the amount of hydrogen penetrating into a metal according to claim 1 or 2, wherein the surface of the specimen on the hydrogen detection surface side is previously coated with Pd, a Pd-containing alloy, or Ni.   The method for measuring the amount of intrusion hydrogen according to any one of claims 1 to 3 is applied to a metal part to be evaluated of a moving body, at least part of which is made of a metal material, and the corrosion of the metal part to be evaluated is accompanied with corrosion. A method for monitoring the amount of hydrogen invading into a metal part of a moving body, wherein the amount of hydrogen entering the inside is continuously measured in a corrosive environment that varies with the traveling environment of the moving body. The amount of hydrogen that enters the metal part of the mobile body according to claim 4, wherein the delayed fracture sensitivity of the metal part is evaluated from the amount of hydrogen that enters the metal part to be evaluated of the mobile body. Monitoring method.

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