JP2007139483A - Corrosion resistance evaluation method of metal material, metal material, and corrosion promotion testing device of metal material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a corrosion resistance evaluation method of metal material simulating an actual environment, the metal material, and a corrosion promotion testing device of the metal material. <P>SOLUTION: Assuming one cycle as repetition of (A) a process of adhering salinity containing chloride ions to a surface of the metal material and (B) a drying process and wetting process of varying and setting the temperature and relative humidity to the metal material, the corrosion resistance of the metal material is evaluated by performing a process constituted by the process of performing at least one cycle one or more times. In the (A) process, the mean particle diameter of salt water adhering to the metal material is 1-300 μm, the salinity adhesion amount is 0.1-10000 mg/m<SP>2</SP>, and the duration is 10 minutes or less. In the (B) process, the dew point fluctuation of the drying process and wetting process is set within ±5°C. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for evaluating corrosion resistance of a metal material used for various products, structures and the like, the metal material, and a corrosion promotion test apparatus for the metal material.

  Metal materials such as surface-treated steel are used in large quantities in home appliances such as OA equipment (copying machines, personal computers, etc.), AV equipment (TVs, videos, etc.), refrigerators, washing machines, and the like. As the types of surface-treated steel materials, there are electrogalvanized steel materials, hot-dip galvanized steel materials, chemical conversion treated steel materials, painted steel materials, and the like. Above all, chrome-treated materials were often used as chemical conversion-treated steel materials, but considering the effect of chromium contained in the chromate-treated material film on the environmental impact, chromate-free surface-treated steel materials were also studied. Already put into practical use. At present, in Japan, chromate materials are almost being replaced by chromate-free surface-treated steel materials.

  On the other hand, with the internationalization of the consumer electronics market, it is expected that product design will be required especially in hot and humid Southeast Asia. In addition, from the viewpoint of environmental conservation and resource conservation, Japanese home appliance industry companies have established the “Green Procurement System” to promote the recycling of home appliances and the reuse of parts. It will be extended. For these reasons, product life design becomes even more important. In addition, the use period has been extended by expanding the use of new materials such as chromate-free surface-treated steel, internationalization of the market, and reuse.

  Product design of metal materials such as surface-treated steel is performed based on the results of exposure tests, but there is a problem that long-term exposure tests require a long time, and depending on the application, it takes a time of 10 years or more. Also, in an environment where home appliances are used, quantitative data is small because the corrosion rate is generally low. In particular, new metal materials such as chromate-free surface-treated steel materials have a short track record of use and no long-term corrosion resistance data. Therefore, in designing products such as home appliances, the importance of a corrosion resistance evaluation method capable of predicting the life of a metal material used for home appliances in a short period is increasing.

  As conventional methods for evaluating the corrosion resistance of metal materials for home appliances, corrosion promotion tests such as a salt spray test and long-term exposure tests in actual usage environments of home appliances have been performed. However, the long-term exposure test has the above-mentioned problems, and the salt spray test is considered to have a low correlation with the actual corrosive environment where home appliances are used, and the correlation with the long-term life is unknown.

  Many combined cycle corrosion test methods combining salt spray, drying and wetting have been developed. However, the conventional combined cycle corrosion test does not properly reproduce the actual environment, and there is still no corrosion acceleration test method that appropriately reproduces the actual corrosion environment. Further, the order of corrosion resistance of materials may be reversed depending on the type of corrosion acceleration test method. This is because the preferred environment differs depending on the metal material.For example, it shows corrosion resistance in a salty environment but has poor corrosion resistance in a low salt environment, and conversely, it does not show corrosion resistance in a salty environment but has a low salt content. This is because there are materials that exhibit corrosion resistance.

  In an environment where home appliances are actually used, thread-like rust occurs on the coated cold-rolled steel sheet, and blisters (blister-like paint film swelling) do not occur on the coated galvanized steel sheet. However, in conventional salt spray tests and combined cycle corrosion tests, the coated cold-rolled steel sheet does not generate thread-like rust, and the coated galvanized steel sheet generates blisters, which can reproduce the corrosive environment of actual home appliances. Not. In actual environments, the coated galvanized steel sheet has better corrosion resistance than the coated cold-rolled steel sheet. In some cases, the corrosion resistance was inferior to that of the steel plate.

  There are also a wide variety of usage environments for home appliances, including outdoor environments with a high salinity, outdoor environments with high temperatures, indoor environments with high humidity, and indoor environments with low salinity and low humidity. It is possible that the corrosion resistance may be insufficient or the quality may be excessive when the product design is evaluated by one type of corrosion acceleration test such as a salt spray test for the use environment.

  On the other hand, several composite cycle corrosion test methods for improving the above problems have been proposed.

  Non-Patent Document 1 proposes an accelerated test method in which salt water is attached to a test piece, and then a wetting process and a drying process in which the dew point temperature is kept constant are repeated. This test method is a cyclic corrosion test in which a wet process (35 ° C., RH 90%) 7 hours—a transition time 1 hour—a drying process (42 ° C., RH 60%) 3 hours—a transition time 1 hour is one cycle.

  In Non-Patent Document 2, a corrosion test is performed that simulates a corrosive environment near the coast where a dew point temperature is kept constant after salt water is attached to a test piece and a wet process and a dry process are repeated. In this test method, the drying process (20 ° C., 65%) 11 hours—the transition time 1 hour—the wetting process (13 ° C., 95%) 11 hours—the transition time 1 hour is one cycle.

  Patent Document 1 proposes an accelerated test method in which salt water is attached to a test piece, and then an actual corrosive environment is simulated to give a continuous temperature change to the test piece to repeat drying and wetting.

Patent Document 2 proposes a corrosion resistance test method for controlling the influence of corrosive environmental conditions by attaching water-soluble salts and solid particles to the surface of a test piece and changing the components and amount of the water-soluble salt.
Japanese Patent Laid-Open No. 10-253524 JP-A-56-79237 VOLVO Corporate Standard STD 1027,1375 (established 1995-06 JB) Materials and Environment Vol. 49, No. 2, p.72 (2000)

  However, in Non-Patent Document 1, the wet process time / (dry process time + wet process time) is as extremely high as 70%, which is different from the environment in which home appliances are used. There was a problem that the phenomenon could not be reproduced.

  In Non-Patent Document 2, when used as a corrosion resistance evaluation method for steel sheets for home appliances, the temperature is low and the acceleration is low, the humidity in the drying process is as high as 65%, and drying is insufficient, and home appliances are used. There was a problem of not simulating the environment.

  According to Patent Document 1, it may be possible to reproduce the target environment, but a test cycle must be set up for each designated environment, which lacks versatility. In addition, there is a problem that the cycle is complicated and it takes time to set the conditions.

In Patent Document 2, the test is performed only in a severe corrosive environment with a large amount of salt (for example, NaCl adhesion amount: 1, 5, 10 mg / cm ² ), and the evaluation in a mild corrosive environment close to the actual environment is described. It has not been.

  The present invention has been made to solve the above problems, and an object thereof is to provide a metal material corrosion resistance evaluation method, a metal material, and a corrosion promotion test apparatus for a metal material that simulate an actual environment. .

Means of the present invention for solving the above-mentioned problems are as follows.
[1] A method for evaluating the corrosion resistance of a metal material by performing the step consisting of the following step (A) and the following step (B) at least once, and in the following step (A), chloride adhering to the metal material The average particle size of the salt water containing ions is 1 to 300 μm, the amount of salt attached is 0.1 to 10000 mg / m ² , and the time required for the following step (A) is within 10 minutes, and the following (B) In the process, the dew point variation between the drying process and the wetting process is within ± 5 ° C.
(A) A step of attaching a salt containing chloride ions to the surface of a metal material (B) One cycle is a repetition of a drying step and a wetting step set by changing the temperature and relative humidity for the metal material. The step [2] of performing this cycle at least once In the step (B) of the above [1], the drying step and the wetting step are performed within the following condition range.
Drying process Temperature: 20-60 ° C., relative humidity: 70% or less, retention time: 2-12 hours Wetting process Temperature: 20-60 ° C., relative humidity: 80-96%, retention time: 2-12 hours [3] In the step (B) of the above [1] or [2], the retention time of the drying step ≧ the retention time of the wetting step.
[4] The method for evaluating corrosion resistance of a metal material according to any one of the above [1] to [3] is performed for two or more levels of the following (C) condition and / or the following (D) condition: To evaluate the corrosion resistance of metallic materials.
(C) In the step (A), a salt adhesion amount condition (D) In the step (B), a condition consisting of a combination of a drying step condition and a wetting step condition [5] The above (4) D) The corrosion resistance evaluation method for a metal material, characterized in that the conditions are the following (E) condition and / or the following (F) condition.
(E) Dew point condition (F) Wetting rate condition represented by the following formula: Wetting rate = (wetting process holding time / (drying process holding time + wetting process holding time))
[6] Corrosion resistance is evaluated at two or more levels by the method for evaluating corrosion resistance of metal materials according to [4] or [5], and based on the evaluation result, the corrosion resistance in an area outside the range between the levels is extrapolated. A method for evaluating the corrosion resistance of a metal material, characterized by being evaluated.
[7] A metal material characterized in that information on corrosion of an actual structure predicted by the method for evaluating corrosion resistance of a metal material according to [6] and / or a symbol indicating the information is attached.
[8] A metal material, wherein electronic information including information on corrosion of an actual structure predicted by the method for evaluating corrosion resistance of a metal material according to [6] is sent to a delivery destination.
[9] A metal material corrosion acceleration test apparatus for performing the method for evaluating corrosion resistance of a metal material according to any one of [1] to [6].

  According to the present invention, the corrosion acceleration test with high-precision control of salt adhesion was performed, and the influence of the dominant environmental factors on the corrosion resistance of the metal material was evaluated. Therefore, the applicable range of the material is clarified. be able to. In addition, the corrosion resistance of the metal material can be evaluated appropriately and with high accuracy in a short-term test. The present invention can be said to be an especially effective invention for designing members such as home appliances.

  Hereinafter, the present invention will be described in detail.

(Embodiment 1)
A method for evaluating the corrosion resistance of a metal material according to the present invention will be described with reference to FIG. FIG. 1 is one of the embodiments of the present invention, and is a diagram illustrating a process of a corrosion acceleration test for performing a corrosion resistance evaluation of a metal material. The corrosion acceleration test shown in FIG. 1 is composed of the following steps (A) and (B), which combine various environmental factors in order to simulate an actual environment. B) The process consisting of processes is performed once or more.
(A) A step of attaching a salt containing chloride ions to the surface of a metal material.
(B) A step of repeating the drying step and the wetting step set by changing the temperature and relative humidity with respect to the metal material as one cycle, and performing this cycle at least once.

  In the step (A), salt water is adhered to the surface of the metal material by spraying the salt water containing chloride ions so that the average particle diameter of the salt water containing chloride ions attached to the metal material is 1 to 300 μm. Let When the average particle size of the adhered salt water exceeds 300 μm, the variation in the test results becomes large. On the other hand, when the average particle size of the salt water is less than 1 μm, it takes time to deposit the salt, and it becomes difficult to control the amount of salt. The test results will vary.

  Conventionally, a salt spray test apparatus has been used, and JIS Z 2371 describes two types of spray tower systems and nozzle systems as examples of salt water spray apparatuses. When this salt spray device is applied to the corrosion promotion test of the present invention, there is a problem that the particle size of the salt water to be adhered varies greatly. In addition, since salt water is supplied by placing test pieces at various locations in the test apparatus, there is a problem that the particle size of sprayed water and the amount of spray vary greatly depending on the position of the test piece and control is difficult. there were.

  On the other hand, for example, FIG. 2 is a diagram showing an embodiment of the method for depositing salt on the metal material surface of the present invention. In the present invention, in a preferred form as a method for depositing salt on the surface of the metal material. is there. In FIG. 2, first, compressed air is sent from the compressor 1 through the air transformer filter 2 to the air brush 3. Next, the airbrush 3 is adjusted to a predetermined nozzle diameter in accordance with the target salt particle size, and the airbrush 3 sprays salt water onto the metal material 5 whose evaluation surface 4 is previously sealed.

  As described above, in the present invention, the method for depositing salt on the surface of the metal material is not particularly limited, but it is important to control the average particle diameter of the salt water adhered to the metal material within the above-mentioned range. For this purpose, it is necessary to adjust the average particle size of the salt water to be adhered by appropriately selecting the spray shape, spray amount, spray pressure, spray angle, spray distance of the spray nozzle, It is preferable to set it as 1-300 micrometers. In addition, the average particle diameter of the salt water before adhering to a metal material can be measured by a liquid immersion method, a laser method (Franhoehel diffraction method, Doppler method), etc. As a method for adhering salt to the surface of the metal material, methods such as salt water spray, salt water immersion, salt water spray, and salt water dripping can be used. Spray nozzles for salt spray include one-fluid spray nozzle (nozzle that sprays liquid that is sent with pressure) and two-fluid spray nozzle (miniaturizes liquid using high-speed fluid such as compressed air) Nozzle). Two-fluid spray nozzles also have a liquid pressurization type (pressurize liquid and supply it to the two-fluid nozzle) and a suction type (spray the liquid by sucking the liquid with the force of compressed air) depending on the liquid supply method. It is preferable to select the spray nozzle from the point that the flow rate distribution becomes uniform. Since salt water is used, the material of the nozzle is preferably a corrosion resistant metal such as stainless steel.

  The average particle size of the attached salt water is obtained by taking out the metal material in a wet state after the step (A), measuring the particle size of the attached salt water by observing with an optical microscope, and determining the average value. . The particle diameter of the adhered salt water is the average value of the maximum diameter and the diameter orthogonal thereto.

  The salt water used for adhering salt to the surface of the metal material includes sea salt or artificial sea salt, sodium chloride, magnesium chloride, calcium chloride, sodium chloride-magnesium chloride mixture, sodium chloride-calcium chloride mixture, rock salt, etc. An aqueous solution can be used. For example, in the environment where home appliances are used, flying sea salt affects the corrosion of the product, so the salt water used is sea salt or artificial sea salt, sodium chloride-magnesium chloride mixture, aqueous solution of sodium chloride. Is preferred.

In the step (A), the amount of salt content including chloride ions attached to the surface of the metal material is 0.1 to 10,000 mg / m ² . This is because by making it within this range, it is possible to cover the salt damage area in the outdoor environment, the area where the salinity is low, and the amount of salt adhesion in the indoor environment. In particular, the amount of salt adhesion in outdoor environments where home appliances such as air conditioner outdoor units are used is in the range of 10 to 10000 mg / m ² when assuming a salt damage area such as Okinawa. Is assumed to be in the range of 1 to 100 mg / m ² , and the amount of salt adhesion when assuming an indoor environment where home appliances such as TVs and VTRs are used should be in the range of 0.1 to 10 mg / m ^2. Is preferred.

  The amount of salt adhesion may be controlled by adjusting the salt water concentration, spray pressure, spray time, and the like. The amount of salt attached is measured by measuring the weight of salt water adhering to the metal material and converting it to the weight of salt water, wiping the metal material surface with absorbent cotton impregnated with distilled water or deionized water, etc. There is a method of analyzing by ion chromatography and converting the Cl concentration to the mass of the salt used.

  Furthermore, in the step (A), the time (hereinafter referred to as “required time”) for attaching the salt containing chloride ions to the surface of the metal material is set to be within 10 minutes. This is because when the test piece is brought into contact with salt water for more than 10 minutes, the corrosion of the test piece by the salt solution may proceed, and the correlation with the corrosion in the actual corrosive environment becomes low.

Next, step (B) will be described.
Process (B) simulates the nighttime dew condensation phenomenon due to the temperature difference between day and night in the actual environment, and takes into account variations and changes in the temperature and humidity control of the test equipment, and the dew point of the drying process and the wetting process. Variation shall be within ± 5 ° C. For example, in FIG. 3, it is desirable to set the dew point constant condition as indicated by condition 1 and condition 2. The curve shown in FIG. 3 indicates the temperature at which the dew point is constant (° C.) and the relative humidity (%), and the dew point is the temperature at which the water vapor pressure in the air is equal to the saturated vapor pressure. is there. Table 1 shows specific conditions of the drying step and the wetting step under the conditions 1 and 2 in FIG.

  As shown in Table 1, the drying process and the wetting process are set to different temperatures and relative humidity. When shifting from the drying process to the wetting process (or moving in the opposite direction), the temperature and relative humidity change. The transition time from the drying process to the wetting process and the transition time from the wetting process to the drying process may be set in advance. This is because when the transition time is not set, the test apparatus may cause a difference in the transition time from the drying process to the wetting process and the transition time from the wetting process to the drying process, resulting in variations in test results. .

  In addition, from the viewpoint of preventing the salt attached in the step (A) from immediately flowing out from the surface of the metal material in the step (B), it is preferable that the step (B) first performs a drying step. Moreover, after drying the salt attached by (A) process previously, you may perform (B) process.

  About the conditions of a drying process and a wet process, in the environment where household appliances are used, it is preferable to set it as the retention time of a drying process> the retention time of a wet process. This is because, assuming an outdoor environment in which home appliances are used or an indoor dry environment, if the wet time becomes longer, the corrosion pattern and corrosion resistance of steel plates for home appliances will not match the actual corrosive environment. . For example, in an environment where home appliances are actually used, thread-like rust is generated on a painted cold-rolled steel sheet, and blisters are not generated on a coated galvanized steel sheet. However, if the retention time of the drying process is less than the retention time of the wet process, the coated cold-rolled steel sheet does not generate thread-like rust, and the coated galvanized steel sheet generates blisters, which corrodes actual home appliances. The form cannot be reproduced.

  In the step (B), in the drying step, the temperature is 20 to 60 ° C., the relative humidity is 70% or less, the holding time is 2 to 12 hours, and in the wetting step, the temperature is 20 to 60 ° C. and the relative humidity is 80. It is preferable to be performed in -96% and holding time: 2-12 hours. This will be described below.

  It is preferable that the drying temperature of a drying process shall be 20 degreeC or more and 60 degrees C or less. This is because, assuming an environment in which home appliances are used, if the drying temperature exceeds 60 ° C., the corrosion pattern and corrosion resistance order of steel plates for home appliances may not match the actual corrosive environment. As a steel sheet for home appliances, a zinc-based plated steel sheet is mainly used, and this has a function of preventing corrosion of iron by sacrificial dissolution of zinc with respect to iron. However, when the temperature exceeds 60 ° C., iron tends to be sacrificed and dissolved in zinc, and a corrosion phenomenon different from the actual environment that rarely exceeds 60 ° C. may be exhibited. On the other hand, if the drying temperature is less than 20 ° C., the effect of promoting corrosion is small and the test takes time. More preferably, it is 40 degreeC or more and 60 degrees C or less.

  The relative humidity in the drying step is preferably 70% or less. In the environment where home appliances are used, flying sea salt affects the corrosion of the product, and the sea salt is mainly composed of sodium chloride and magnesium chloride. The saturated critical vapor pressure of sodium chloride is about 75 to 78% in terms of relative humidity and dries below 80%, but the saturated critical vapor pressure of magnesium chloride is about 30 to 35% in terms of relative humidity and is included in sea salt. It is the lowest chemical substance and is difficult to dry. Therefore, when assuming an outdoor environment in which home appliances are used or an indoor dry environment, the relative humidity in the drying process is set to 70% or less in order to reproduce the corrosion pattern of steel sheets for home appliances in a real environment. It is preferable. More preferably, it is 40% or less.

  The temperature of the wetting process and the relative humidity may be set so that the dew point variation with respect to the conditions of the drying process is within ± 5 ° C., but the temperature is preferably 20 ° C. or more and 60 ° C. or less. If the temperature is less than 20 ° C., the effect of promoting corrosion is small and the test takes time. On the other hand, when the temperature exceeds 60 ° C., iron tends to be sacrificed and dissolved in zinc, and a corrosion phenomenon different from the actual environment in which the temperature does not easily exceed 60 ° C. may be exhibited.

  The relative humidity in the wetting step is preferably 80% or more and 96% or less. This is because if the relative humidity in the wetting process is less than 80%, the influence of wetting is insufficient and evaluation takes time. Among chlorides, sodium chloride has a saturated critical vapor pressure of about 75 to 78% in terms of relative humidity. Accordingly, when any chloride is kept at a relative humidity of 80% or more, the surface can be kept wet by the chemical condensation action. On the other hand, when the relative humidity exceeds 96%, the water film thickness generated by the condensation becomes too thick, and the attached salt becomes easy to flow.

  It is preferable that the holding time of the drying step and the wet step is 2 hours or more and 12 hours or less. If the holding time of the drying process and the wet process is less than 2 hours, the corrosive environment in one test apparatus is not constant, the test results vary greatly depending on the location in the test apparatus, This is because differences may occur and variations in test results may occur. On the other hand, if it exceeds 12 hours, it will not match the actual corrosive environment, and it will take a long time to evaluate the corrosion resistance.

  In addition, when it is necessary to consider the effects of sunlight exposure and sulfur oxides regarding environmental factors, an ultraviolet irradiation step and a sulfur oxide (SOx) supply step should be added to the atmosphere during the corrosion acceleration test. You can also.

(Embodiment 2)
Since the influence of environmental factors on the corrosion resistance of metal materials varies depending on the type of metal material, it is desirable to conduct a corrosion acceleration test by changing the environmental factors and examine the corrosion resistance characteristics of each metal material. FIG. 4 is a graph showing the relationship between the amount of deposited salt and the amount of corrosion during a certain test period of the corrosion acceleration test, taking the amount of deposited salt as an environmental factor. Moreover, the amount of corrosion here refers to the swollen width (or simply swollen width) of the coating film, the amount of corrosion of the galvanized or base steel material, and the like. From FIG. 4, the slope of the straight line of the relationship between the amount of corrosion and the amount of corrosion of the metal materials No. 1, No. 2 and No. 3 is different, and the order of the amount of corrosion of the metal materials No. 1, No. 2 and No. Have been replaced. Thus, performing a corrosion acceleration test at one level may make a mistake in the judgment of corrosion resistance evaluation. Therefore, it is preferable to conduct a corrosion acceleration test by changing the level of environmental factors to examine the corrosion resistance characteristics of the metal material. For example, (C) condition: salt adhesion amount condition in step (A), (D) condition: condition consisting of a combination of drying process condition and wetting process condition in process (B), or (C) condition And (D) It is preferable to evaluate the corrosion resistance of the metal material for two or more levels of conditions.

  As other conditions, in the step (A), the corrosion resistance evaluation may be performed on two or more levels of salt content, number of times of deposition, time, and temperature.

(D) Conditions: In the step (B), the conditions comprising the combination of the drying process conditions and the wetting process conditions include (E) dew point conditions, drying process temperature, humidity, holding time, and wetting process temperature. , Humidity, holding time combination, and (F) wettability conditions. Here, the wet rate is expressed by the following equation.
Wetting rate = (wet process holding time / (dry process holding time + wet process holding time))
Among these, (E) dew point condition and (F) wet rate condition are preferable because they are often dominant environmental factors in the actual environment, and are therefore preferred in terms of examining their influences. (E) condition and / or (F) condition It is preferable to perform corrosion resistance evaluation for two or more levels.

  In the method for evaluating the corrosion resistance of the metal material of the present invention, it may be performed for two or more levels of conditions appropriately selected from the above-described conditions. The choice of conditions can be determined according to whether it becomes a dominant environmental factor. The dominant environmental factor is a condition whose condition level affects the corrosion resistance (corrosion amount or corrosion life) of the material.

  For example, when the dominant environmental factor is the amount of salt attached, the amount of salt attached in the step (A) is evaluated with at least two levels. When the dominant environmental factor is temperature, the temperature of the drying step and the temperature of the wetting step in the step (B) are evaluated at at least two levels. When the dominant environmental factor is the wet rate, the (F) wet rate condition is performed under the condition of at least two levels. In the case where the dominant environmental factors are the amount of salt adhesion and temperature, the amount of salt adhesion in step (A): (C) the condition is at least two levels, and the temperature of the drying step and the temperature of the wetting step in (B) are also at least What is necessary is just to carry out by the combined condition which made it 2 levels or more and changed both conditions. In this case, it may be performed for each combination condition obtained above, or may be performed under a plurality of conditions selected from the conditions combined above from the viewpoint of reducing the test load.

  When the dominant environmental factors are the amount of salt and the wet rate, the amount of salt attached in step (A): (C) the condition is at least two levels, and the rate of wetness in step (B): (F) the condition is at least 2 What is necessary is just to carry out by the combined condition which made it more than the level and changed both conditions.

  With the above-described method for evaluating the corrosion resistance of a metal material, in the present invention, it is possible to further evaluate the corrosion resistance in a region outside the range between levels at the time of evaluation. Specifically, first, the corrosion resistance is evaluated under two or more levels by the metal material evaluation method of the present invention. Next, the corrosion resistance at a level (region) outside the range between levels at the time of evaluation is predicted and evaluated by extrapolating based on the evaluation result. The actual corrosive environment may be milder than conventional corrosion accelerated test methods. For example, the salt adhesion amount in an actual corrosive environment is often smaller than the salt adhesion amount in the corrosion acceleration test. Therefore, it is preferable to conduct a corrosion acceleration test with a small amount of salt, but there is a problem that the corrosion rate is low and the evaluation takes time. Therefore, a corrosion acceleration test is performed by setting a salt adhesion amount of at least two levels including a condition with a large salt adhesion amount, and the corrosion amount in an environment with a small salt adhesion amount can be extrapolated and predicted.

  FIG. 5 is a schematic view showing a change in corrosion amount with time when a corrosion promotion test is performed with a certain level of salt adhesion amount a, b, c set for a certain material. FIG. 6 is a schematic diagram showing the relationship between the amount of adhered salt and the amount of corrosion during the test periods t1, t2, t3, and t4 based on FIG. From FIG. 5 and FIG. 6, it is possible to extrapolate the corrosion amount for each test period in the salt adhesion amounts a, b, and c to predict the corrosion amount of the salt adhesion amount d. FIG. 7 is a schematic diagram showing the change over time in the corrosion amount of the salt adhesion amount d predicted based on the above result.

  Further, the corrosion life can be predicted by extrapolating the corrosion life of each test period in the same manner as the amount of corrosion. FIG. 8 is a schematic diagram showing the relationship between the salt adhesion amount and the corrosion life, taking the salt adhesion amount as an example based on the results of FIGS. 5 and 6. Incidentally, the corrosion life means the time (for example, the time when the swollen width of the coating film reaches 5 mm, etc.) for reaching the corrosion amount threshold in the change in appearance (such as rust generation time) and the time-dependent change in the corrosion amount in FIG. .

  In this way, based on the corrosion resistance evaluation results performed at two or more levels, the corrosion resistance of metal materials such as the amount of corrosion and corrosion life can be estimated by extrapolating and predicting the corrosion resistance at a level (region) outside the range between the levels at the time of evaluation. Information can be obtained. When the evaluated metal material is used for each part (hereinafter referred to as an actual structure) such as an actual machine, corrosion information of the actual structure is obtained, and information predicting corrosion and / or the information. It is possible to attach a symbol indicating to a metal material.

(Embodiment 3)
By using the method for evaluating corrosion resistance of a metal material according to the present invention, it is possible to order, manufacture, and sell a metal material that predicts the progress of corrosion of an actual structure.

FIG. 9 is a flowchart showing an example of a steel surface treatment process. According to FIG. 9, the following processes in (S61) to (S67) are performed.
(S61) Steel material degreasing step: Oil and dirt adhering to the surface of the steel material before coating are removed.
(S62) Steel material polishing step: The oxide film on the steel material surface is removed with a brush to activate the surface. The chemical conversion processability of the post process is improved.
(S63) Chemical conversion treatment step: Phosphate treatment, chromate treatment, chromate-free treatment, etc. are performed. There is a pre-treatment role to improve paint film adhesion and a functional role to improve the corrosion resistance of steel. When the life of a steel material can be predicted by the method for evaluating corrosion resistance of a metal material of the present invention, and when a longer life is expected, it can be reflected in this chemical conversion treatment.
(S64) Painting process: A process of coating a paint. Roll coating and spray coating are common.
(S65) Baking process: drying and curing of paint, formation of paint film. Depending on the required corrosion resistance, painting and baking may be repeated a few times.
(S66) Inspection process: Inspects pinholes, uneven gloss, color tone, etc. of the coating film.
(S67) Protective film attaching step: There are cases where the protective film is not applied, but there are cases where the protective film is attached and shipped upon request from the customer.

  Information on the corrosion of the actual structure predicted by the method for evaluating corrosion resistance of a metal material of the present invention and / or a symbol indicating the information is attached to the surface-treated steel material manufactured as described above. In addition, this attachment includes not only mechanical attachment but also a case where the surface-treated steel material and its information are associated with each other. For example, it is preferable to add information (e.g., data relating to the expansion width of the steel material) at the time of evaluating the corrosion resistance or a symbol indicating the information to the surface-treated steel material. It is also preferable to send the information or data related thereto as electronic information to a delivery destination. This electronic information may be a recording medium such as an FD, or may be sent (transmitted) to a delivery destination via a network.

(Embodiment 4)
In the second embodiment, an example in which the amount of attached salt is the dominant environmental factor has been described. However, the dominant environmental factor of the present invention is not limited thereto. In an environment surrounded by the four sides of the ocean, such as in Japan, the amount of salt deposits has a strong correlation with corrosion as the dominant environmental factor, but in extreme inland areas and indoor environments, temperature is the dominant environmental factor. Or humidity is the dominant environmental factor. Also, sulfur oxides may be the dominant environmental factor in the limited areas of the city. Even in such an environment, the method for evaluating the corrosion resistance of the metal material of the present invention is effective, and the corrosion resistance of the metal material can be easily evaluated in a short period of time.

  Specifically, when the temperature is the dominant environmental factor, the temperature setting of the process of repeating the drying process and the wet process may be changed, and when the humidity is the dominant environmental factor, the drying process and the wet process are changed. What is necessary is just to change the humidity of the process to repeat, or to change a moisture rate. Hereinafter, this point will be described with reference to FIGS.

FIG. 10 shows the conditions of the drying process and the wetting process when the conditions of the drying process and the wetting process are standard conditions as a standard type. In FIG. 10, the temperature is shown on the horizontal axis, the relative humidity is shown on the vertical axis, and the numerical values in parentheses for the drying process and the wet process are attached to the arrows of both sides of the line connecting the drying process and the wet process. The numerical values in parentheses indicate the transition time when transitioning to each of the above steps, the former being 3 hours, and the latter being 1 hour.
When temperature is the dominant environmental factor, the conditions of the process of repeating the drying process and the wetting process are set to a low temperature type condition as shown in FIG. 11 in addition to the standard type. That is, according to FIG. 10, only the temperature is set to a low temperature with respect to the standard type, and the influence of the temperature can be examined by comparing the two conditions. In both the standard mold and the low temperature mold, the dew point temperature fluctuation in the drying process and the wet process in each mold is set within ± 5 ° C.

  When the wetting rate is the dominant environmental factor, the conditions of the process of repeating the drying process and the wetting process are set to the high-wetting type conditions as shown in FIG. That is, in the standard type shown in FIG. 10, the wet process time is 3 hours, the dry process time is 3 hours, and the wet rate (wet process holding time / (dry process holding time + wet process holding time)) is 50%. However, according to FIG. 12, in the high wet type, the wet process time is set to 5.5 hours, the dry process time is set to 0.5 hours, the wet rate is 70%, and the ratio of the wet process time is increased. Yes. And the influence of a wetting rate can be investigated by comparing these two. In both the standard type and the high-humidity type, the dew point temperature fluctuation in the drying process and the wet process in each mold is set within ± 5 ° C.

  In the above embodiment, the case where there is one dominant environmental factor has been described. However, the present invention can also be applied to cases where the dominant environmental factor is two or more. For example, in coastal areas where humidity is high, the amount of salt and temperature may be two dominant environmental factors.

  Moreover, in this embodiment, the example which performed the corrosion resistance evaluation of surface-treated steel materials using the swollen width of the coating film as corrosion resistance data was demonstrated. However, in this invention, it is not limited to this, Corrosion resistance evaluation can also be performed based on these using the external appearance change of a surface-treated steel material, a white rust generation | occurrence | production area, etc. as corrosion resistance data.

  Specific conditions when there are two or more combinations of drying and wetting processes are exemplified below.

  FIG. 13 is a diagram illustrating an example of test conditions for setting the test conditions of the process of repeating the drying process and the wet process to three levels and examining the influence of temperature. In FIG. 13, the temperature of each condition is shown in the upper stage, and the relative humidity of each condition is shown in the lower stage. The same applies to FIGS. 14 to 16 described below. Table 2 shows specific conditions for each of the drying step and the wetting step in FIG.

  FIG. 14 is a diagram illustrating an example of test conditions for setting the test conditions of the process of repeating the drying process and the wetting process to three levels and examining the influence of relative humidity. Table 3 shows specific conditions of each step of the drying step and the wetting step in FIG.

  FIG. 15 is a diagram illustrating an example of test conditions for setting the test conditions for the process of repeating the drying process and the wetting process to three levels and examining the influence of the dew point. Table 4 shows specific conditions of the drying process and the wetting process in FIG.

  FIG. 16 is a diagram showing an example of test conditions for setting the test conditions of the process of repeating the drying process and the wetting process to three levels and examining the influence of the wetting rate. Table 5 shows specific conditions of each step of the drying step and the wetting step in FIG.

(Embodiment 5)
In the above-described third embodiment, the corrosion resistance evaluation of the coated steel material as the surface-treated steel material has been described. However, the metal material of the present invention is not limited to the coated steel material, and includes a chemical conversion treatment steel material and a plating treatment steel material. In addition, the present invention is applicable to steel materials such as weathering steel materials and metal materials such as non-ferrous metal materials used in a corrosive environment.

  FIG. 17 is a diagram showing the secular change of each treated steel material. In FIG. 17, (A) corresponds to a coated steel material, (B) corresponds to a chemical conversion treated steel material, and (C) corresponds to a plated steel material. As shown in FIG. 17A, the coated steel material 6 is obtained by sequentially forming a plating layer 10, a chemical conversion treatment layer 11, and a coating film 12 on a steel 9. According to FIG. 17A, since the coating film 12 has higher corrosion resistance than the plating layer 10 or the like, before the coating film 12 changes over time, the plating layer 10 changes over time, and the cut end is oxidized and whitened. Rust 13 is formed, and the portion is expanded, and the cut end of the coating film 12 is expanded. The width W from the end portion of the swelled coating film 12 is referred to as a bulge width, which is a parameter indicating the degree of corrosion. Moreover, as shown in FIG. 17B, the chemical conversion treatment steel material 7 is obtained by sequentially forming the plating layer 10 and the chemical conversion treatment layer 11 on the steel 9. According to FIG. 17B, since the chemical conversion treatment layer 11 has low corrosion resistance, when the plating layer 10 is exposed due to corrosion, the plating layer 10 is oxidized and becomes white rust 13. Moreover, the plating-treated steel material 8 is obtained by forming a plating layer 10 on a steel 9 as shown in FIG. According to FIG. 17C, the plating layer 10 is oxidized to white rust 13, and when the plating layer 10 is peeled off, the steel 9 is oxidized and red rust 14 is generated.

  Thus, the coating steel material 6, the chemical conversion treatment steel material 7, and the plating treatment steel material 8 each change over time, and the appearance life thereof is in the relationship of the life of the coating steel material> the life of the chemical conversion treatment steel material> the life of the plating treatment steel material. Therefore, since the present invention is useful when applied to the life prediction of a steel material having a long life, it can be said that the usefulness is particularly remarkable when applied to a chemical conversion treated steel material and a coated steel material.

(Embodiment 6)
FIG. 18 is a diagram showing an example of the configuration of a corrosion acceleration test apparatus for performing the corrosion resistance evaluation method for a metal material of the present invention. The corrosion acceleration test apparatus according to the present invention includes a salt adhesion apparatus and a dry and wet test apparatus. In FIG. 18A, the salinity adhering device and the drying / wetting test device are integrated, and the salinity adhering is performed periodically, and then the drying step and the wetting step are repeated. In FIG. 18B, the salt adhesion apparatus and the dry / wet test apparatus are arranged side by side, and the object to be tested (metal material) is automatically placed between the salt adhesion apparatus and the dry / wet test apparatus periodically. Moving. In FIG. 18 (C), the salt adhesion apparatus and the dry / wet test apparatus are separate apparatuses, and the specimen (metal material) is periodically manually placed between the salt adhesion apparatus and the dry / wet test apparatus. Moving.
As described above, the configuration of the corrosion promotion test apparatus of the present invention is not particularly limited, but (A) a salt content containing chloride ions is attached to the surface of the metal material, which is an essential process for evaluation. The process, and (B) the metal material, the drying process and the wet process set by changing the temperature and relative humidity are set as one cycle, and the process of performing this cycle at least once is implemented. It is essential.

Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to these.
(Examples 1-12, Comparative Examples 1-8)
For the chromate-treated steel sheet (100 mm × 100 mm), a corrosion resistance evaluation test was performed in which a salt adhesion process, a drying process, and a wetting process were sequentially performed on three chromate-treated steel sheets for each condition under the conditions shown in Tables 6 to 8. . The salt water adhesion step was performed at the start of the drying step. Moreover, when providing the transition time between a drying process and a wet process, it showed in the remarks column of a table | surface. The test period was 7 days. After the salt water adhesion and after the test, the salt water adhesion state and the corrosion state on the surface of the test piece were observed. Here, the salt water spray used a liquid pressurization type two fluid spray nozzle, and the particle size of the atomized salt water containing the sprayed chloride ions was measured by the Doppler method to obtain the average particle size. In addition, the test piece immediately after spraying in the first salt adhesion step is taken out, and the particle size of the attached salt water is observed with an optical microscope at 10 points of salt water adhering part per test piece. The average of was obtained. In addition, the amount of salt attached is that the test surface of one metal specimen after the first salt attachment is wiped with absorbent cotton impregnated with deionized water, this absorbent cotton is immersed in deionized water, and the eluted Cl concentration Was measured by ion chromatography and calculated from the test area.

  Table 10 shows the obtained results.

  As shown in Table 10, in the inventive examples of Examples 1 to 12, the salt water adhesion of the three test pieces was uniform. On the other hand, in Comparative Examples 1-8, salt water adhesion was non-uniform | heterogenous and the variation between three test pieces was large. Further, in the inventive examples of Examples 1 to 12, the appearance of the three test pieces after the corrosion test, that is, the corrosion state was uniform, but in Comparative Examples 1 to 8, it was non-uniform and between the three test pieces. The variation was large. From the above results, it can be seen that by using the evaluation method of the present invention, the influence of the amount of salt adhesion can be evaluated appropriately and with high accuracy.

(Example 13)
FIG. 19 is a diagram showing test conditions for a corrosion acceleration test in which the amount of adhering salt is set to 3 levels. As a salt adhesion method, salt water spray using a liquid pressurizing type two-fluid spray nozzle was performed once every 84 hours, and salt water to be used was prepared by diluting artificial seawater. Artificial seawater has three levels of salt water concentration (mass%) of 3.5%, 0.35%, and 0.035%, and the salt deposits are 0.6, 0.06, and 0.006 g / m ² , respectively. It was made to become. Further, the process of repeating the drying process and the wetting process was assumed to have a constant dew point, and a transition time of 1 hour was set between drying and wetting.

FIG. 20 shows the swollen widths and test times of the coated steel materials A, B, and C obtained by the corrosion acceleration test under the conditions shown in FIG. 19 (salt water concentration 3.5%: salt adhesion amount 0.6 g / m ² ). It is a figure which shows the relationship. Such data was created for each test condition.
FIG. 21 is a diagram showing the relationship between the swollen widths of the coated steel materials A, B, and C on the test period 28 and the amount of salt attached. It can be seen that the amount of corrosion increases as the amount of adhered salt increases, and the logarithm of the amount of adhered salt and the logarithm of the swollen width of the coating film have a good linear relationship. Further, the swollen width corresponding to the salt adhesion amount can be obtained. For example, the swollen width of the coated steel materials A, B, and C when the salt deposit amount is 0.1 g / m ² is 0.9, 1.7, 0, respectively. .5 mm. Here, a straight line can be extrapolated even in a range where the corrosion rate is low and the amount of salt adhesion which takes a long time to evaluate, for example, the swollen width of the coated steel materials A, B and C when the salt adhesion amount is 0.001 g / m ² . Are 0.02, 0.05, and 0.1 mm, respectively.
In this way, it is possible to perform an appropriate corrosion resistance evaluation of a steel sheet for home appliances or the like based on a corrosion test condition that simulates the environment in which the home appliance is used. And it can also grasp | ascertain the corrosion-resistance evaluation corresponding to the amount of salt adhesion of the environment where the target household appliances are used.

(Example 15)
Under the same test conditions as in Example 14, the corrosion promotion test was performed by changing the salt content of the 3 levels to 4 levels, and the corrosion resistance of the chemical conversion treated steel materials A, B, and C was evaluated. Here, the salt water concentration (mass%) of the artificial seawater is four levels of 3.5%, 0.35%, 0.035%, and 0.0035%, and the salt adhesion amounts are 0.6, 0.00, respectively. 06, 0.006, and 0.0006 g / m ² .
FIG. 22 is a diagram showing the relationship between the amount of salt and the number of days of white rust occurrence of the chemical conversion treated steels A, B, and C. The test period is up to 60 days, and no white rust is generated in 60 days under the condition of a salt adhesion amount of 0.0006 g / m ² for the chemical conversion treated steel material C. It can be seen that the larger the amount of adhered salt, the shorter the number of days in which white rust occurs, and the logarithm of the amount of adhered salt and the logarithm of days of white rust have a good linear relationship. Here, the chemical conversion treatment because the steel C White rust is not generated in 60 days under the condition of Salt Adhesion 0.0006 g / m ² for the white based on the salt deposition intensive conditions results (3 points) Rust The generation time can also be extrapolated.
In this way, not only can corrosion assessment conditions that simulate the environment in which home appliances are used be used, it is possible to perform appropriate corrosion resistance evaluation of steel plates for home appliances, etc., but the corrosion rate is low and the evaluation takes time due to the small amount of salt. Even in the case, the evaluation can be made by extrapolating from the test results under conditions with a large amount of salt adhesion.

  When applying the metal material evaluation method of the present invention, the application range is not limited and can be widely used. In addition, since the metal material of the present invention is attached with corrosion information based on the corrosion test conditions simulating the environment in which the home appliance is used, for example, OA equipment (copying machine, personal computer, etc.), AV equipment (TV, video, etc.) ), A useful material for home appliances such as refrigerators and washing machines.

It is one of the embodiment of this invention, and is a figure which shows the process of the corrosion acceleration test for performing the corrosion resistance evaluation of a metal material. It is a figure which shows one embodiment of the salt adhesion method to the metal material surface of this invention. It is a figure which shows the conditions of the drying process of the corrosion acceleration test of this invention, and a wetting process. It is the figure which showed the relationship between the salt adhesion amount and the corrosion amount in a certain test period of a corrosion acceleration test. It is the schematic diagram which showed the time-dependent change of the corrosion amount in each salt adhesion amount when a corrosion acceleration test was done. It is the schematic diagram which showed the relationship between the salt adhesion amount and corrosion amount in test period t1, t2, t3, t4. It is the schematic diagram which showed the time-dependent change of the corrosion amount in each salt content including the estimated salt content d. It is the schematic diagram which showed the relationship between the amount of salt adhesion, and the corrosion life. It is a flowchart figure which shows an example of the process of the surface treatment of steel materials. It is a figure which shows the conditions of the standard type of a drying process and a wet process. It is a figure which shows the conditions of the process of repeating a drying process and a wetting process in case temperature is a dominant environmental factor. It is a figure which shows the conditions of the process of repeating a drying process and a wetting process in case humidity is a dominant environmental factor. It is a figure which shows an example of the test conditions for setting the test conditions of the process of repeating a drying process and a wet process to 3 levels, and investigating the influence of temperature. It is a figure which shows an example of the test conditions for setting the test conditions of the process of repeating a drying process and a wet process to 3 levels, and investigating the influence of relative humidity. It is a figure which shows an example of the test conditions for setting the test conditions of the process of repeating a drying process and a wet process to 3 levels, and investigating the influence of dew point humidity. It is a figure which shows an example of the test conditions for setting the test conditions of the process of repeating a drying process and a wetting process to 3 levels, and investigating the influence of a wetting rate. It is a figure which shows the secular change of a coating steel material, a chemical conversion treatment steel material, and a plating treatment steel material. It is a figure which shows one embodiment of the corrosion acceleration test apparatus of this invention. It is a figure which shows the test conditions of the corrosion acceleration test which set the salt adhesion amount to 3 levels. (Example 2) It is a figure which shows the relationship between the swelling width of coating steel materials A, B, and C, and test time. (Example 2) It is a figure which shows the relationship between the swelling width of the coated steel materials A, B, and C of the test period 28 days, and the amount of salt adhesion. (Example 2) It is a figure which shows the relationship between the amount of salt adhesion, and the white rust generation | occurrence | production days of chemical conversion treatment steel plates A, B, and C. (Example 2)

Explanation of symbols

1 Compressor 1
DESCRIPTION OF SYMBOLS 2 Air transformer filter 3 Air brush 4 Evaluation surface 5 Metal material 6 Painted steel material 7 Chemical conversion treatment steel material 8 Plating treatment steel material 9 Steel 10 Plating layer 11 Chemical conversion treatment layer 12 Paint film 13 White rust 14 Red rust

Claims (9)

It is a method for evaluating the corrosion resistance of a metal material by performing the process consisting of the following (A) process and the following (B) process at least once,
In the following step (A), the average particle diameter of salt water containing chloride ions attached to the metal material is 1 to 300 μm, the amount of salt attached is 0.1 to 10,000 mg / m ² , and the following step (A) Travel time is less than 10 minutes,
Furthermore, in the following step (B), the dew point variation between the drying step and the wetting step is within ± 5 ° C. A method for evaluating the corrosion resistance of a metal material.
(A) A step of attaching a salt containing chloride ions to the surface of a metal material (B) One cycle is a repetition of a drying step and a wetting step set by changing the temperature and relative humidity for the metal material. , The process of performing this cycle at least once In the said (B) process, a drying process and a wetting process are performed within the following condition range, The corrosion resistance evaluation method of the metal material of Claim 1 characterized by the above-mentioned.
Drying process Temperature: 20-60 ° C., relative humidity: 70% or less, retention time: 2-12 hours Wetting process Temperature: 20-60 ° C., relative humidity: 80-96%, retention time: 2-12 hours   3. The method for evaluating corrosion resistance of a metal material according to claim 1 or 2, wherein in the step (B), the retention time of the drying step is equal to or greater than the retention time of the wetting step. A method for evaluating the corrosion resistance of a metal material according to any one of claims 1 to 3 with respect to two or more levels of the following (C) condition and / or the following (D) condition: Corrosion resistance evaluation method.
(C) Salt content amount condition in the step (A) (D) Condition consisting of a combination of a drying step condition and a wetting step condition in the step (B) The said (D) conditions in Claim 4 are the following (E) conditions and / or the following (F) conditions, The corrosion resistance evaluation method of the metal material of Claim 4 characterized by the above-mentioned.
(E) Dew point condition (F) Wetting rate condition represented by the following formula: Wetting rate = (wetting process holding time / (drying process holding time + wetting process holding time))   The corrosion resistance evaluation method of the metal material according to claim 4 or 5 is evaluated for corrosion resistance at two or more levels, and based on the evaluation result, the corrosion resistance in a region outside the range between the levels is extrapolated and evaluated. To evaluate the corrosion resistance of metallic materials.   7. A metal material to which information on corrosion of an actual structure predicted by the method for evaluating corrosion resistance of a metal material according to claim 6 and / or a symbol indicating the information is attached.   7. A metal material, wherein electronic information including information on corrosion of an actual structure predicted by the method for evaluating corrosion resistance of a metal material according to claim 6 is sent to a delivery destination. A corrosion promotion test apparatus for a metal material for performing the corrosion resistance evaluation method for a metal material according to any one of claims 1 to 6.

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