JP2003215024A - Method for predicting amount of corrosion of metallic material due to galvanic corrosion, life predicting method, metallic material, structure designing method, and method for manufacturing metallic material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for predicting the amount of corrosion and life of a metallic material due to galvanic corrosion capable of highly accurately predicting galvanic corrosion, the metallic material related to the method, a structure designing method, and a method for manufacturing the metallic material. <P>SOLUTION: The method for predicting the amount of corrosion and life of the metallic material due to galvanic corrosion comprises a process for measuring both a current which passes when two types of metal pieces S1 and S2 joined via an insulating member 1 are externally brought into contact with each other and its transition with the passage of time and a process for predicting the progress of corrosion of the base metal S2 among the two types of metal pieces S1 and S2 on the basis of the transition of the current with the passage of time measured in the measuring process. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of predicting the amount of corrosion and life of a metal material due to contact corrosion of different metals, a metal material,
The present invention relates to a method of designing a structure and a method of manufacturing a metal material.

[0002]

2. Description of the Related Art In a structure having a portion where two different kinds of metals come into contact with each other, a phenomenon in which a base metal part of the two kinds of metals is preferentially corroded is called a dissimilar metal contact corrosion and is often called a structure. Seriously damage. There is an example of measuring and analyzing the corrosion rate of such dissimilar metal contact corrosion in an environment immersed in seawater or the like.

[0003]

However, there has been no conventional technique for measuring the corrosion rate of contact corrosion of dissimilar metals in the atmospheric environment. The atmospheric environment in corrosion is a thin water film environment formed on a dissimilar metal, and since the whole is not immersed in an aqueous solution like an immersion environment, it is difficult to construct an electrochemical model. The model in seawater could not be applied directly. Therefore, it is impossible to quantitatively obtain the corrosion rate of the contact corrosion of dissimilar metals in the atmospheric environment because it depends exclusively on experience and know-how.

The present invention has been made in order to solve the above-mentioned problems, and it is possible to predict the corrosion of dissimilar metal contacts with high accuracy, and the corrosion amount and life of the metal material due to the contact corrosion of dissimilar metals. An object of the present invention is to provide a prediction method, a related metal material, a structure design method, and a metal material manufacturing method.

[0005]

(1) A method for predicting the amount of corrosion of a metal material due to the contact of dissimilar metals according to one aspect of the present invention,
Based on the step of measuring the current flowing when the two kinds of metal pieces joined via an insulating material are brought into external contact and the time-dependent transition thereof, and the time-dependent transition of the current measured in the step, Of the two kinds of metal pieces, a step of predicting the progress of corrosion of a base metal is included. The metallic material in the present invention includes a metallic material to be applied to a component, a member, and a component / member.

(2) A method of predicting the amount of corrosion of a metal material due to contact between different metals according to another aspect of the present invention is the same as the method of predicting the amount of corrosion of (1) above, in which a plurality of the two kinds of noble metals having different areas are used. Prepare the metal pieces of, and measure the current flowing to the outside for each of the two kinds of metal pieces, and find the maximum current among them.
The current flows when the two types of metal pieces are brought into external contact.

(3) A method of predicting the amount of corrosion of a metal material by contacting different kinds of metals according to another aspect of the present invention is to bring two kinds of metal pieces joined together through an insulating material into external contact in a plurality of actual environments. Of the two kinds of metal pieces based on the first step of measuring the current flowing when the electric current flows and its time course, and the time course of the current measured in the first step,
A second step of predicting the progression of base metal corrosion in a plurality of real environments; and a third step of measuring environmental factors near or around the two kinds of metal pieces in the plurality of real environments, A fourth step of predicting the progress of corrosion in the environmental factors based on the environmental factors in the plurality of actual environments and the prediction of the progress of corrosion.

(4) A method for predicting the amount of corrosion of a metal material due to contact between different metals according to another aspect of the present invention, wherein in the method for predicting the amount of corrosion in (3) above, when there are a plurality of environmental factors, the environmental factors The one having a relatively large correlation coefficient between the corrosion amount and the corrosion amount is set as a dominant environmental factor, and the progress of corrosion in the dominant environmental factor is predicted in the fourth step.

(5) A method for predicting the amount of corrosion of a metal material due to the contact between different metals according to another aspect of the present invention is the method for predicting the amount of corrosion of a metal material as described above in (3) or (4), in which the target real structure or its actual structure As a reference value, the corrosion amount measured at a reference position provided in or on the surface of a structure simulating the structure (hereinafter referred to as an actual structure or the like), or a reference position provided outside the actual structure or the like, Corrosion amount measured at each site in the actual structure and the like, when the ratio of the reference value is the site coefficient, based on the site coefficient and the correspondence between the reference value and a predetermined environmental factor, The amount of corrosion of each part such as the actual structure in an area different from the measurement area is calculated.

(6) In the method of predicting the amount of corrosion of a metal material caused by the contact between different metals according to another aspect of the present invention, in the method of predicting the amount of corrosion of (5), the predetermined environmental factor is the amount of incoming sea salt. .

(7) In the method of predicting the amount of corrosion of a metal material due to the contact between different metals according to another aspect of the present invention, in the method of predicting the amount of corrosion of the above (3) to (6), the measurement of the environmental factor is at least 1 month

(8) A method of predicting the amount of corrosion of a metal material due to the contact between different metals according to another aspect of the present invention is the method of predicting the amount of corrosion of any of the above (3) to (7), wherein the environmental factor is flying sea salt. Amount, temperature, humidity, sunlight dose or SOx.

(9) A method for predicting the amount of corrosion of a metal material caused by contact between different metals according to another aspect of the present invention, wherein the method for predicting the amount of corrosion in any of the above (3) to (8) is preliminarily evaluated when predicting the amount of corrosion. Execute this after dividing the area to be divided into areas with similar environment.

(10) In the method of predicting the amount of corrosion of a metal material caused by contact with different metals according to another aspect of the present invention, data indicating the relationship between environmental factors and the progress of corrosion of the metal material caused by contact corrosion of different metals is obtained in advance. In advance, the corrosion amount of the metal material due to the contact corrosion of dissimilar metals in the actual structure or the like is predicted based on the data and the environmental factors in the planned construction area of the target actual structure.

(11) A method for predicting the amount of corrosion of a metal material due to contact corrosion of dissimilar metals according to another aspect of the present invention is described in (1) above.
In the corrosion amount prediction method of 0), the predicted value of the corrosion amount of the metal material due to the contact corrosion of different kinds of metals in each area is made into a database.

(12) A method for predicting the life of a metal material due to corrosion of a dissimilar metal contact according to another aspect of the present invention is the method for predicting the corrosion amount of a metal material according to any one of (1) to (11) above. Predict the life of metallic materials based on the amount of corrosion predicted in.

(13) A method of predicting the life of a metal material by contact corrosion of dissimilar metals according to another aspect of the present invention is described in (12) above.
In the method of predicting the service life, the service life is predicted by calculating the amount of metal thinning corresponding to the joint structure of two kinds of metals.

(14) A metal material according to another aspect of the present invention comprises a set of metal materials whose life is predicted by the life prediction method of (12) or (13) above, and the progress of corrosion of each part. The data at the time of forecasting is attached.

(15) A metal material according to another aspect of the present invention is the metal material according to the above (14), to which the data or a symbol indicating the data is added.

(16) In the metal material according to another aspect of the present invention, in the metal material according to (14) or (15), the data or data related thereto is sent to the delivery destination as electronic information.

(17) A method of designing a structure according to another aspect of the present invention is a method for designing a structure from one or more sets of metal materials whose corrosion progress is predicted by the life prediction method of (11) or (12) above.
Select a metal material to be applied to the actual structure.

(18) In the method for manufacturing a metal material according to another aspect of the present invention, the metal material designed by the method of designing a structure according to (17) above is manufactured.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1. FIG. 2 is a diagram for explaining the phenomenon of contact corrosion of dissimilar metals. When the noble metal S1 and the base metal S2 come into contact with each other, a potential distribution as shown in the figure occurs between the two. When the water film 10 is formed on the noble metal S1 and the base metal S2 so as to extend over them,
A current circuit is formed, and a current having a distribution as illustrated flows between the noble metal S1 and the base metal S2. It is known from the example of the seawater model that the base metal part S2 of the two kinds of metals is corroded by the flow of this current, and the amount of corrosion depends on the current (dissimilar metal corrosion current) flowing in the noble metal S1. Has been.

FIG. 1 is a block diagram of a sensor utilizing the phenomenon of contact corrosion of dissimilar metals in FIG. By inserting the insulating member 11 between the noble metal S1 and the base metal S2,
Prevent current from flowing directly between and. The insulating member 11 is for insulating between the metals S1 and S2,
It is desirable to be as thin as possible. In addition, an ammeter (galvanic ammeter) 1 is provided between the noble metal S1 and the base metal S2.
2 is connected and the current flowing when both are brought into external contact is measured. As is clear from the description of FIG. 1, it is desirable to measure the current flowing between the metals S1 and S2, but since it cannot be measured, the metal S
1 and S2, an insulating member 10 is inserted, and an electric current flowing therethrough is made to flow to an ammeter (galvanic ammeter) 12, and the water film 10 is arranged so as to straddle the metals S1 and S2.
When is formed, a current (dissimilar metal corrosion current) flows through the ammeter (galvanic ammeter) 12.

FIG. 3 shows the precious metal S1 in the sensor of FIG.
Of a plurality of areas (lengths) prepared in order to obtain the relationship between the area (length) and the corrosion currents of dissimilar metals S1a to S1
It is explanatory drawing of 1c. By measuring the current flowing through the ammeter 12 for each of the plurality of areas (lengths) S1a to S1c of the noble metal S1 shown in FIG.
The distribution (maximum current imax, length 1) of the dissimilar metal corrosion current flowing in the noble metal S1 is obtained. In the first embodiment, since the width A of the noble metals S1a to S1c is constant, the area and the length are synonymous.

FIG. 4 is a characteristic diagram showing the relationship between the area (length) of noble metal and the corrosion current of different metals. As shown in the figure, when the area (length: l) of the metal exceeds a predetermined value, the dissimilar metal corrosion current saturates and the maximum value becomes constant (the maximum value of this dissimilar metal corrosion current is (Corresponding to the shaded area of 1). Since the corrosion amount of the base metal S2 depends on its maximum value, it can be seen that the area (length) of the noble metal S1 in the sensor of FIG. 1 may be a predetermined area (length) or more.

FIG. 5 is a characteristic diagram showing changes in the characteristics of FIG. 4 with time. Water film 10 formed on the sensor of FIG.
When the corrosion product is generated over time, the conductivity thereof becomes low, and the maximum value (imax) of the dissimilar metal corrosion current becomes small over time.

FIG. 6 is a characteristic diagram showing the relationship between the number of years (exposure time) and the maximum value of the different metal corrosion currents of FIG.
By plotting the maximum value of FIG. 5 over time and converting it into an appropriate linear model (regression equation), a characteristic expression showing the relationship between the elapsed years and the maximum value of the dissimilar metal corrosion current can be obtained. it can. In this way, the characteristic diagram of FIG. 6 is obtained,
A predicted value for the maximum value of corrosion currents of dissimilar metals over the future is required.

FIG. 7 is a characteristic diagram showing the relationship between the elapsed years and the amount of corrosion. Here, the amount of corrosion is calculated based on the maximum value of the corrosion currents of different metals, but the following process is performed in the calculation.

Imax decreases with time, imax = at ^b (1) where a and b are constants determined from imax measured with time, and −1 ≦ b <0. Further, the quantity of electricity C is given by C = ∫imax (t) dt = a / (b + 1) × t ^{(b + 1)} (2)

Using Faraday's law, ΔW = M / n · C / F ΔW: mass loss (corrosion amount) M: atomic weight n: valence F: Faraday constant = 96485 [C / g] To be ΔW increases with time, and is expressed by the following formula: ΔW (t) = M / n · C / F = (M / nF) × a / (b + 1) × t ^{(b + 1)} (3) It

By obtaining ΔW: mass loss, that is, the amount of corrosion as described above, a predicted value of the amount of corrosion in the future can be obtained. Based on this predicted value of the amount of corrosion, the precious metal S1
It is possible to predict the service life of the joint structure between the base metal S2 and the base metal S2.

In the first embodiment, the noble metal S1 and the noble metal S2 are described without specifying them, but the two have a relative relationship, and for two kinds of metals for which the relationship holds, In any case, the first embodiment is applied.

Embodiment 2. FIG. 8 is a flow chart showing the processing steps of the design method, the manufacturing method, etc. of the metal material and the like according to the second embodiment of the present invention. The second embodiment is a further development of the measurement principle of the first embodiment.

(S11) The amount of corrosion in each area (A, B, C ...) Is estimated by the sensor shown in FIG.
The characteristics of are calculated for each region. Here, for example, the amount of corrosion of stainless steel as the noble metal, iron as the base metal, and various other combinations are estimated.

FIGS. 9A to 9C show each area (A, B,
It is a characteristic view when estimating the corrosion amount in a certain 2 kinds of dissimilar metal contact in C).

(S12) Environmental factors of each area (A, B, C ...) Are measured. As environmental factors, for example, the amount of flying sea salt,
There are temperature, humidity, etc., but these are each area (A, B, C
...) for a predetermined period (at least one month or more) for each time to obtain an average value.

FIG. 10 is a diagram showing an example in which environmental factors (average values) measured in each area (A, B, C ...) Are listed.

It is assumed that the area is classified into coastal areas, mountainous areas, urban areas, and the like. When making a prediction, it is preferable to classify the surveyed area into areas of similar environment to some extent. The similar environment means an area where the temperature or the change of the temperature is similar, an area where the change of the humidity or the temperature is similar, or the like. Taking Japan as an example, it is classified into Hokkaido, the Okinawa Nansei Islands, and the Pacific coast. If divided and evaluated in this way, the life can be predicted easily and in a short period of time, and the accuracy of prediction can be improved.

(S13) The dominant environmental factors are determined by classifying and quantifying the environmental factors. In this step, environmental factors such as the amount of incoming sea salt, temperature, and humidity are collected from the above-described data (FIGS. 9 and 10), the environmental factors are plotted against the amount of corrosion, and the calculation processing described later is performed. By determining the correlation coefficient (coefficient of determination) of both, it is determined that the one with a relatively large correlation coefficient (coefficient of determination) is the dominant environmental factor that controls the corrosion rate. .

FIG. 11 is a characteristic diagram showing the relation between the amount of incoming sea salt and the amount of corrosion. From the above-mentioned data (FIGS. 9 and 10), for example, when the elapsed years in FIG. 9 are 3 years and 5 years, By extracting the amount of corrosion and further extracting the amount of flying sea salt in each region from FIG. 10, the relationship between the amount of flying sea salt and the amount of corrosion with the elapsed years of 3 years and 5 years as a parameter is obtained. Also, the other elapsed years shall be similarly obtained. Further, regarding the temperature and the humidity, the characteristics similar to those in FIG. 11 are obtained, and the following processing is performed.

Here, a method of determining the dominant environmental factor will be specifically described. Environmental factors (independent variables) X and corrosion amounts (dependent variables) Y are each logarithmized and converted into a linear model for regression analysis. Further, the correlation coefficient (determination coefficient) R ² of the equation (3) is calculated by the following equation (4). logY = α + βlogX (3)

[0043]

[Equation 1]

In obtaining the constants α and β in the above equation (3), the amounts of incoming sea salt, humidity, temperature, etc., which are environmental factors, are obtained. In the example of FIG. 11, for example, applying the corrosion amount and the amount of incoming sea salt after 5 years to the above formula (3),
The above-mentioned constants α and β are obtained, and the correlation coefficient (determination coefficient) thereof is obtained. Further, the correlation coefficient is similarly obtained for humidity, temperature, and the like.

When the correlation coefficients (coefficients of determination) of the amount of incoming sea salt, humidity and temperature are obtained as described above, the mutual coefficients are compared and the coefficient of determination shows the largest value. Determine the factor as the dominant environmental factor. The following Table 1 is an example of the correlation coefficient of each environmental factor when the noble metal is stainless steel and the base metal is aluminum.

[0046]

[Table 1]

After determining the dominant environmental factors, the constants α and β of the above equation (3) for the environmental factors are obtained for at least 3 years (for example, 3 years, 5 years, 10 years). (It is desirable that there are many minutes for this year).

(S14) The sensors shown in FIG. 1 are installed at a plurality of target parts of a target real structure (or a structure imitating the structure), and the current (imax) is measured. In this process, since the environment is microscopically different in the actual structure, the corrosion rate of each part is quantified with respect to the external environment. Since the climate of Japan has four seasons and changes greatly in one year, it is desirable to measure continuously for one year, but even one-month measurement can be sufficiently estimated from climate data in each region of Japan. Is.

In the measurement, for example, the sensor of FIG. 1 is used to measure the actual structure requested by the customer or a plurality of parts of the structure simulating the actual structure. Depending on the site (for example, in the body or in a narrow place), there is a place where the amount of incoming sea salt cannot be measured.
And the measurement by the sensor of FIG. 1 are performed in parallel, and only the measurement of the sensor of FIG. Since the output of the sensor of FIG. 1 can be quantified, the degree of environmental data (for example, the amount of incoming sea salt, temperature, humidity, etc.) can be estimated from the output of the sensor of FIG. 1 as shown in the following equation (5). Actually, 1 outdoors
The corrosion rate is 0.2 for the part A, and the corrosion rate is 0.01 for the part B.

[0050]     Coefficient of part = Corrosion amount of part / Corrosion amount of outdoor… (5)

FIG. 12 is a diagram showing the site coefficient of each site measured above, where the outdoor area is 1, and the site 1 is
It can be seen that the regions 3 have different values.

Here, for example, the actual structure will be described as an example of a housing member such as a prefab or a steel house. Data on the amount of incoming sea salt and data on the amount of corrosion of metal materials will be taken in a one-month test. On the other hand, the amount of corrosion of each used part such as the eaves, the back of the hut, and the inside of the wall is measured by the sensor of FIG. From the relationship between the amount of incoming sea salt and the amount of corrosion measured outdoors, the site coefficient is obtained by the above equation (5), so that the area (for example, Okinawa) different from the area (for example, Hokkaido) measured above can be used in the above area. When installing a structure similar to, calculate the amount of corrosion at each site using the site coefficient.

(S16) Next, a dissimilar metal corrosion map is prepared based on the nationwide meteorological data already measured. Here, the amount of incoming sea salt in an area not measured above (excluding areas A to Z) is obtained from a database of existing meteorological data, and the amount of different metal corrosion in that area is obtained and made into a database. For example, if it is found that the amount of incoming sea salt in a certain area is a (mdd), the change over time in the amount of corrosion at each site is predicted based on the amount of incoming sea salt a and the above-mentioned site coefficient. The unit mdd for the amount of incoming sea salt is mg / dm ² · day (10 cm × 1
The amount of sea salt captured per day in an area of 0 cm square).

Specifically, the amount of incoming sea salt at each part (for example, the amount of incoming sea salt at each part such as outdoors, eaves, attic, back wall, etc.)
Are applied to the characteristics shown in FIG. 11 to obtain data on the amount of corrosion and the number of years elapsed. In the example of FIG. 11, for example, when the environmental factor is the amount of incoming sea salt a (mdd), the amounts of corrosion Ya3, Ya5, and Ya10 corresponding thereto are calculated. Then, the logarithms of the elapsed years (independent variable) T and the corrosion amount (dependent variable) Y are taken, converted into a linear model, and regression analysis is performed to obtain constants γ and δ. logY = γ + δlogT (7)

FIG. 13 is a characteristic diagram conceptually showing the relationship between the number of years elapsed and the corrosion amount in the outdoor areas 1 to 3 obtained by the above equation (7).

By obtaining the above-mentioned data for each area, a dissimilar metal corrosion map is created and stored as a database. In this case, data on combinations of various kinds of different metals should be similarly obtained. By creating a database in this way, for example, by extracting environmental factors from the weather data of the area where construction is planned,
The amount of corrosion of the target structure can be easily obtained from the environmental factors and the above database.

(S17) A structure is designed based on the above different metal corrosion map. Here, the corrosion amount of each part of the corresponding structure is obtained from the above-mentioned dissimilar metal corrosion map,
Furthermore, the life (useful life) is obtained from the structure of the part.

Here, the predicted corrosion amount is ΔW [g], and the predicted corrosion amount per unit area is ΔW1 [g /
m ² ], ΔW1 is expressed by the following equation. Δ W1 [g / m ² ] = Δ W [g] / (width of metal piece × l) (8) l: length of noble metal when maximum current flows in FIG.

The predicted corrosion amount ΔW1 [g / m ² ] is generated by the area multiple (A1) of the noble metal and is consumed by the area (A2) of the base metal portion, so the amount of thinning ΔT [ m] can be calculated by directly allocating the area of the corroded portion of the base metal. The basic formula is as follows, where ρ [g / m ³ ] is the density of the base metal. ΔT = ΔW1 × A1 / A2 / ρ (9)

Next, ΔT when the contact portion is a straight line and a circular arc will be described. (1) When the contact portion is a straight line ΔT = ΔW1 × (l × A) / (L × A) / ρ (10) However, L [m] and A [m] are defined in FIG. Note that FIG. 14 is a view showing a plane when the noble metal S1 and the base metal S2 are joined.

Here, a method for obtaining the above L [m] will be described. In the same manner as described in the first embodiment, the current distribution (length of maximum current) of the base metal S2 is calculated. FIG. 15 is an explanatory diagram at that time. Metal pieces (test pieces) S1a to S1c having different lengths for the noble metal S1 and the base metal S2, respectively.
S2a to S2c are prepared, and the current when the both are externally connected is measured by the ammeter 12. Precious metal S
A metal piece (test piece) having a different length is prepared for each of the 1 and the base metal S2, and the current when the both are externally connected is measured by the ammeter 12. Base metal S
Also in No. 2, as in the case of the noble metal S1, the current value increases as the length increases, and the value saturates at the predetermined length L. The length L is applied to the design of the actual structure as L in the above equation (10) and the equation described later.

(2) When the contact portion is an arc: In FIGS. 16A and 16B, the arc metal material is the base metal S2.
It is explanatory drawing of a structure in the state where the noble metal S1 has covered the outer periphery, and has shown the case where the radius r is larger than L and the case where the radius r is smaller than L, respectively. (A) When the radius r of the arc is larger than L, the amount of wall thinning Δ
T is ΔT = ΔW 1 × π ((r + 1) ² −r ² ) / π (r ² − (r−L) ² ) / ρ (11) (b) When the radius r of the arc is smaller than L, The amount of thickness reduction ΔT is ΔT = ΔW1 × π ((r + 1) ² −r ² ) / πr ² / ρ (12)

The amount of wall thinning ΔT is determined by the above calculation,
The service life (service life) can be determined based on the allowable amount of metal thinning such as the strength of each structure.

(S18) By the above processing, the specifications of the metal material or parts satisfying the product conditions can be obtained. Next, the process of manufacturing and selling the metal material will be described. (S18a) The metal material is selected. Here, the material is selected from among the metal materials that have been filled with the service life (for example, 30 years) by the above processing.

In the above processing (S17), for example, when all the metal materials for which the life is predicted do not satisfy the service life, the corrosion resistance is obviously higher than that of the metal material for which the prediction is made. It is also possible to select a known metal material. Corresponding relationships can be established to some extent for metal materials of the same system, so for example, a metal material of the same system and with high corrosion resistance as the metal material predicted to have the longest life may be selected.

Further, for example, when all the metal materials for which the life has been predicted do not satisfy the service life, a new metal material may be designed based on the prediction result. If minor design modifications are made to a metal material, it is used that the degree of improvement in corrosion resistance can be predicted. It is conceivable to change the thickness of the metal material whose life is to be predicted, for example, to change the type of chemical conversion treatment, to change the temperature control in the baking process, or to change the plating adhesion amount.
Note that in the present invention, the concept of designing includes all of material selection, material selection, and material design.

(S18b) Orders, manufactures, and sells materials.

The metal material manufactured as described above includes
The data of the above processing (S16) and / or (S17) is attached. Note that this attachment includes not only mechanical attachment but also the case where the metal material and its data are associated with each other in some way. For example, the data at the time of predicting the progress of corrosion of each of the above parts or a symbol indicating the data is added to the metal material, or the data or data related thereto is sent as electronic information to the delivery destination. This electronic information is F
It may be a recording medium such as D or may be sent (transmitted) to the delivery destination via a network.

In the first embodiment, as described above,
By grasping the dominant environmental factors, it has become possible to quantitatively and accurately obtain the progress of corrosion of metal materials such as metal materials. It is ready to be put out. In the past experience,
Since such a treatment could not be performed, only a qualitative suggestion as to the corrosion amount and life of the actual structure could be suggested.

Embodiment 3. In the above embodiment, an example in which the amount of flying sea salt is the predominant environmental factor has been described, but the predominant environmental factor of the present invention is not limited thereto. In an environment surrounded by a four-sided sea like Japan, the amount of incoming sea salt has a strong correlation with corrosion as a dominant environmental factor, but in the extremely limited inland area, temperature is the dominant environmental factor, Humidity may be the dominant environmental factor. Sulfur oxides may also predominate in the very limited areas of the city. Even in such an environment, the present invention is effective, and the life expectancy of a metal material can be easily predicted in a short period of time. Further, in the above embodiment, the case where there is one dominant environmental factor has been described, but the present invention can be applied to the case where there are two or more dominant environmental factors.
For example, in coastal regions with high humidity, the amount of incoming sea salt and humidity may be the two dominant environmental factors.

The environmental factors include the amount of incoming sea salt, the temperature, the humidity, the amount of sunlight (the amount of ultraviolet irradiation), etc.
Corrosion factors are measured by the gauze method, thermometer, hygrometer, and ultraviolet ray meter for these environmental factors.

Embodiment 4. In addition, although the life prediction of the metal material and the like have been described in the above-described first embodiment, in the present invention, other metal materials such as a plated material are included as long as the metal causes a problem of dissimilar corrosion.

[0073]

As described above, according to the present invention, the current flowing when two kinds of metal pieces joined via an insulating member are brought into external contact and the transition thereof with time are measured, and the current is measured with time. Since the progress of corrosion of the base metal of the two kinds of metal pieces is predicted on the basis of the dynamic transition, it is possible to accurately predict the long-term corrosion amount of the metal material.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a sensor utilizing a phenomenon of contact corrosion of dissimilar metals.

FIG. 2 is a diagram for explaining a phenomenon of contact corrosion of dissimilar metals.

FIG. 3 is an explanatory diagram of a plurality of types of areas (lengths) prepared for obtaining the relationship between the area (length) of the noble metal S1 and the dissimilar metal corrosion current in the sensor of FIG.

FIG. 4 is a characteristic diagram showing the relationship between the area (length) of noble metal and the corrosion current of dissimilar metals.

FIG. 5 is a characteristic diagram showing changes over time in the characteristics of FIG.

6 is a characteristic diagram showing the relationship between the number of years elapsed (exposure time) and the maximum value of the dissimilar metal corrosion current of FIG.

FIG. 7 is a characteristic diagram showing the relationship between elapsed years (exposure time) and the amount of corrosion.

FIG. 8 is a flowchart showing processing steps of a design method, a manufacturing method, and the like of a metal material and the like according to a second embodiment of the present invention.

FIG. 9 is a characteristic diagram when the amount of corrosion in contact with two specific kinds of dissimilar metals in each region (A, B, C) is estimated.

FIG. 10 is a diagram showing an example in which environmental factors (average values) measured in each area (A, B, C ...) Are listed.

FIG. 11 is a characteristic diagram showing the relationship between the amount of incoming sea salt and the amount of corrosion.

FIG. 12 is a diagram showing the site coefficient of each site measured above.

FIG. 13 is a characteristic diagram conceptually showing the relationship between the number of years elapsed and the amount of corrosion in the outdoor areas 1 to 3.

FIG. 14 is a view showing a plane when a noble metal S1 and a base metal S2 are joined.

FIG. 15 is an explanatory diagram for obtaining a current distribution (maximum current, length when the maximum current flows) for the noble metal S1 and the base metal S2.

FIG. 16 is a noble metal S2 in which the arc-shaped metal material is the base metal S2.
It is explanatory drawing of the state in which 1 has covered the outer periphery.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G01N 27/416 G01N 27/46 301M (72) Inventor Sakae Fujita 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Steel Tube Co., Ltd. F term (reference) 2G050 AA01 BA02 BA04 BA06 BA09 BA10 CA01 DA02 EA01 EA02 EA03 EB02 EC05 4K060 AA02 BA13 BA14 BA39 DA07 DA10 EB02 FA07

Claims (18)

[Claims] 1. A step of measuring a current flowing when two kinds of metal pieces joined via an insulating material are brought into external contact with each other and a transition thereof with time, and a step of measuring the current measured in the step with time. And a step of predicting the progress of corrosion of a base metal of the two kinds of metal pieces on the basis of the transition. 2. A plurality of the two kinds of metal pieces having different noble metal areas are prepared, and an electric current flowing to the outside of each of the two kinds of metal pieces is measured, and the maximum current among them is measured. Two
The method for predicting the amount of corrosion of a metal material due to contact corrosion of dissimilar metals according to claim 1, characterized in that a current that flows when the seed metal piece is brought into external contact is used. 3. A first step of measuring a current flowing when two kinds of metal pieces joined via an insulating material are brought into external contact in a plurality of actual environments, and a transition thereof with time, The second step of predicting the progress of corrosion of a base metal in a plurality of actual environments among the two kinds of metal pieces based on the change over time of the electric current measured in the first step and the plurality of the pieces of metal. In the environment, based on the third step of measuring the environmental factors near or around the two kinds of metal pieces, and the environmental factors in the plurality of actual environments and the prediction of the progress of corrosion, corrosion in the environmental factors And a fourth step of predicting the progress of the above method. 4. When there are a plurality of environmental factors, the one having a relatively large correlation coefficient between the environmental factors and the amount of corrosion is defined as a dominant environmental factor, and in the fourth step, the dominant environmental factor is used. The method for predicting the amount of corrosion of a metal material due to the contact corrosion of different metals according to claim 3, which predicts the progress of corrosion in. 5. A reference position provided in or on a surface of a target real structure or a structure simulating the real structure (hereinafter referred to as a real structure or the like), or provided outside the real structure or the like. When the corrosion amount measured at the reference position is the reference value, and the ratio between the corrosion amount measured at each part of the actual structure or the like and the reference value is a part coefficient, the reference value and the predetermined environmental factor Based on the correspondence relationship with and the site coefficient,
The method for predicting the amount of corrosion of a metal material due to the contact corrosion of different metals according to claim 3 or 4, wherein the amount of corrosion of each part of the actual structure or the like in an area different from the measurement area is obtained. 6. The method of predicting the life of a metal material by contacting different metals according to claim 5, wherein the predetermined environmental factor is the amount of incoming sea salt. 7. The method of predicting the amount of corrosion of a metal material due to the contact corrosion of dissimilar metals according to claim 3, wherein the environmental factor is measured for at least one month. 8. The metal material according to any one of claims 3 to 7, wherein the environmental factor is the amount of incoming sea salt, temperature, humidity, sunlight dose, or SOx. Corrosion amount prediction method. 9. The metal according to any one of claims 3 to 8, wherein when estimating the amount of corrosion, the region to be evaluated is divided into regions having similar environments and then the corrosion is performed. A method for predicting the amount of corrosion of materials. 10. Data indicating the relationship between environmental factors and the progress of corrosion of metallic materials due to contact corrosion of dissimilar metals is obtained in advance, and the data and environmental factors in the planned construction area of the target actual structure or the like. The corrosion amount of the metal material due to the contact corrosion of the dissimilar metals in the actual structure or the like is predicted based on the above, and the corrosion amount of the metal material due to the contact corrosion of the dissimilar metals according to any one of claims 3 to 9. Prediction method. 11. The method for predicting the amount of corrosion of a metal material by contact corrosion of different metals according to claim 10, wherein the predicted value of the amount of corrosion of the metal material by contact corrosion of different metals in each region is stored in a database. . 12. Corrosion corrosion of dissimilar metals, characterized in that the life of a metal material is predicted based on the amount of corrosion predicted by the method of predicting the amount of corrosion of a metal material according to any one of claims 1 to 11. Method for predicting the life of metallic materials. 13. The method of predicting the life of a metal material by contact corrosion of dissimilar metals according to claim 12, wherein the amount of metal thinning corresponding to the joint structure of two kinds of metals is calculated to predict the life. 14. A set of metal materials, the life of which is predicted by the method of life of a metal material by contact between different kinds of metals according to claim 12 or 13, wherein data for predicting the progress of corrosion of each part is Metal material characterized by being attached. 15. The metal material according to claim 14, wherein the data or a symbol indicating the data is added. 16. The metal material according to claim 14, wherein the data or data related thereto is sent to a delivery destination as electronic information. 17. A metal material for application to an actual structure is selected from one or more sets of metal materials whose corrosion progress is predicted by the method for predicting life of a metal material according to claim 11 or 12. Method of designing structures. 18. A method for manufacturing a metal material, which comprises manufacturing a metal material designed by the method for designing a structure according to claim 17.